Why do lens manufacturers produce lenses with few aperture blades?

Question

A lot of lenses have very few aperture blades (especially budget lenses). A large number of aperture blades can make a real difference to the bokeh and seems like it should be a priority for the lens manufacturers to me. If the cost of adding a few more blades is low it would seem like a cheap and easy way to improve the value of a lens.

I get that a more intricate design will be more expensive, but will the addition of a few extra blades really add a lot of cost to the whole lens? Is it mostly a marketing trick perhaps to add apparent value to the more expensive lens alternatives? Is there another reason I've missed perhaps?

Answer 1

Well, single blade itself isn't very expensive, I guess. But the additional blades require more blade mounting mechanisms and its cost is more likely significant.

Moreover, always take marketing into account. Main goal of lens manufacturer is income, not better quality for lower price. Diversification of lenses helps the business running. Let's consider for example Nikon prime 50mm lenses. You can have the f1.8G with seven diaphragm blades for 200$ and f1.4G with nine diaphragm blades for 350$. If you absolutely want to have nine diaphragm blades, would you pay for more expensive f1.4G if cheaper f1.8G had nine blades too? I doubt.