Sometimes it makes sense, but it does not always make sense. It all depends on what you want to do with the camera and lens. It really does depend.
Your pictures will never be better optically than the lens that projects the light onto the sensor. But the performance of the sharpest lens in the world is mostly wasted on a noisy, low resolution sensor. There IS some degree of the need for each piece of the puzzle to be complimentary of the other. But that doesn't mean a lens and a body well suited for each other to do a particular job will both cost about the same. Far from it.
For most casual shooters or amateurs who never generate any income from their photography an entry level body is good enough. At the entry level the lenses are generally cheaper than the bodies. This may lead a lot of folks just venturing into ILC and DSLR-land to think the camera is more important than the lens when it comes to image quality and should always cost more than the lenses one hangs on the body. Nothing could be further from the truth.
Other than sensor size, which we'll get to in a moment, bodies are distinguished from one another by features and build quality, not differences in image quality. Within most manufacturers product lines all of their APS-C sensors have about the same image quality. As you move up the product line you get more direct controls that allow faster handling. You get faster frame rates and deeper memory buffers, which allow faster handling. You get more configurable AF systems that are (hopefully) more accurate and consistent that give you a higher "keeper" rate of fast moving subjects. You get better protection from the elements and other hazards that can damage your camera that allows you to shoot under less than ideal conditions without trashing your gear. You get sturdier, more durable bodies that can take more knocks and abuse without breaking. But you don't usually see much image quality difference among APS-C cameras of the same generation from the same manufacturer. The same is true, to a lesser extent, with full frame sensors. There are a wider range of resolutions available between the lowest and highest resolution FF bodies, but when images are displayed at typical viewing conditions there aren't that many differences between cameras under that same makers' umbrella and in the same technological generation. There is a demonstrable difference between FF sensors and APS-C or smaller sensors with the same technology, especially when shooting moving subjects in low light.
Lenses, on the other hand, improve more incrementally starting from the cheapest kit zoom lenses through the mid-grade, enthusiast, and pro lines. And while there are certainly exceptions to the rule, when comparing prime lenses to other prime lenses or zoom lenses to other zoom lenses higher priced lenses in the same focal length range with image circles designed for the same sized image sensor are generally better optically than their lower priced counterparts as well as built to be more rugged and durable. Due to the increased cost of such lenses, reliability is more of a concern for buyers as a good lens should last decades beyond even the liberal five or six year warrantee that some lenses now carry. There are a few lenses that have great optics placed in housings with not so great build quality, but they are generally the exception rather than the rule.
For $900 you can get a lot better normal zoom such as a 17-50/55mm f/2.8 than a $100* 18-55mm f/3.5-5.6. But it is not 9x as good of a lens by most ways of reckoning. And to get that much improvement again, one would need to spend far more than another $800 or maybe even a LOT more than $8,100 (9x). See Canon CN-E 14.5-60mm T2.6 L S Cinema Zoom Lens with EF Mount.
(*The EOS SL1 currently sells body-only for $400, the 18-55 kit lens sells alone for $200, but the kit price for both, at $500, is only $100 more than the body.)
The way I look at lenses is not so much how far above a "zero" starting point they are as it is how close to a perfect "100%" do they reach? A decent modern 18-55mm kit lens might be somewhere around a "75%" on my arbitrary "percentage of perfection" scale. That's a passing grade, but at 25% away from 100% there is still a lot of room for improvement. A 17-50mm f/2.8 costing several hundred dollars more may be somewhere around an "85%". That extra 10 points cost a lot more! But the 85% lens is only about half as far from a perfect 100% as the 75% lens is. The next step up might be something like the $2,000 EF 24-70mm f/2.8 L II (because a lens of that grade is almost certainly going to be for FF cameras and 24-70mm will give roughly the same field of view on a FF camera as a 17-50 will on an APS-C body). Say it is a 92% lens. That additional 7% added another $1,100 to the price. You could also say to get half as close to 100% you had to spend twice as much. To get to 96%, that CINE lens we referenced above runs about $43,000! 20x as much for either a 4% gain or to get half as close to 100%, depending on which way you look at it.
I say all of that to say this: As the quality of a lens approaches an idealized expectation, the costs of designing, producing, and owning such a lens grows exponentially.
The same is true of many things: A $30K car is a lot nicer than a $15K car, but it probably won't go twice as fast. To get there you probably need to look at an $80-120K vehicle. To get another 20-30% beyond that in terms of top speed, you're talking about spending millions of dollars for something like a McLaren or a purpose built F1 racer!
Putting it all together
So how much should we spend on cameras and how much should we spend on lenses?
There's no correct answer that fits everyone. Some need better bodies. Others need better lenses. Some need both. Some need neither.
One shooter may be perfectly happy with an entry level body and kit lens. The body is roughly 70% of that equation for a 2:1 ratio in favor of the body. Throw in a cheap telephoto and it goes to about 50/50.
Another shooter may be interested in fast sports action in bright daylight. A consumer grade zoom such as a 70-300mm f/4-5.6 that runs about $500 may be optically good enough but a body with very good AF and fast handling is going to run around $1,300. We're now in a 3:1 ratio in favor of the body, even though we've spent three times as much in total as we did for the entry level body and kit lens. But what if he needs that same reach under stadium lighting at night? The same body will do but now a $3.6K 120-300mm f/2.8 lens is called for. The ratio just shifted to 3:1 weighted towards the lens! And if you need to go beyond 300mm with any kind of fast aperture the lenses get very expensive very fast.
Someone else may need to capture ambient light photographs in very low light without using flash. That may call for a FF camera such as the 6D ($1,400) but a fast prime lens like the EF 50mm f/1.8 STM ($125) may be all of the lens needed. That's an 11:1 body ratio! But if we throw in the need to have focal lengths all the way from 24-70mm and only enough time to change lenses once or twice, the equation changes very quickly. That EF 24-70mm f/2.8 L II ($2,000) plus the EF 50mm f/1.8 STM (125) for when it is really dark has now shifted the ratio to 3:2 in favor of the lens.
Now let's look at a working photojournalist on staff at a mid sized newspaper. Her gear takes a pounding day in and day out, but it has to be dependable and just work. So she probably has a $5K pro body and perhaps another $2.5K backup body. In terms of lenses she also must be able to cover pretty much everything from ultra wide angle (EF 16-35mm f/2.8 L II / $1.5K), to normal (EF 24-70mm f/2.8 L II / $2K), to short telephoto (EF 70-200mm f/2.8 L IS II / $2K), to long telephoto (EF 400mm f/2.8 L / $8K in 1998 dollars when her newspaper bought it - it's still good and the bean counters can't justify replacing it with the $10K replacement). And then there's a set of good (but not great) primes: $1.1K 35mm f/1.4 (v.1 see note on 400mm above), $350 50mm f/1.4, $370 85mmf/1.8, and a good $600 100mm f/2.8 Macro. Anything else will need to be checked out from the photo room's specialty lens cabinet for a particular assignment. She's driving around with about $8K worth of cameras and $16K worth of lenses in her trunk. So we're back to about a 2:1 ratio weighted towards the lenses again just to get her through a typical working week. And we haven't even started talking about lights and modifiers for feature assignments, fashion assignments, a couple of shoots for the ad department (oh wait, newspapers aren't selling ads any more!), and photo illustrations yet!
In the end the cost of a camera body and the cost of a lens aren't that related. DSLRs range in price from around $400 to $6,000 new. Lenses run anywhere from about $100 to $12,000 before you start getting into exotic or CINE territory. So the spread between the extremes in terms of bodies is only about 15x while the spread between lenses is much greater at 120x. The cheapest bodies are about 4x as much as the cheapest lenses, but the most expensive (non-exotic) lenses cost around twice the price of the most expensive (still image oriented 35mm/FF) bodies.
If you need or just want the image quality of an expensive lens but don't need the low light gathering capabilities of a full frame sensor, the ruggedness of a pro grade body, or the bells & whistles of an advanced APS-C body then it makes perfectly good sense to spend a lot more on a lens than on a camera body.
But just because that makes sense for one photographer doesn't mean it will make sense for all.