The "$26,000 lens" is the Sigma 200-500mm/2.8 APO DG, and it usually weighs in at around $30,000 retail (depending on the retailer, country of purchase and exchange rates). There is a reason for that.
A prime 500mm/2.8 lens (a lens that isn't a zoom) would come in at around $15,000 with decent glass and corrections. The front element would need to be just over seven inches (about 18cm) across, and a lens consists of a lot more than a single element. At long focal lengths, making all of the various colours focus at the same point (eliminating lateral chromatic aberration) is a lot more critical than at shorter focal lengths, otherwise your images will look like old-fashioned red/blue 3D prints/movies without the 3D glasses. Once you start adding in extra elements to correct for all of the various flaws that are inherent to refractive optics (lenses) -- and some of those elements need to be made from outrageously expensive materials that are incredibly dificult to work with -- and add the precision mechanics it takes to keep all of those elements in the right relationship to each other as you focus, the cost of the lens really doesn't sound all that bad.
Making it zoom out to 200mm while keeping it acceptably rectilinear, APO corrected, parfocal (a "true zoom", rather than just a lens with an adjustable focal length) and constant-aperture takes a lot more glass and precision mechanics. And let's not forget that this particular lens is also a 400-1000mm/5.6 zoom: the 2x "teleconverter" that comes with this baby is not an off-the-shelf item; it is an integral part of the lens's design.
Really, $30,000 or so isn't so bad if you make your living using lenses like this one. If you ever get to see it in person and pick it up, you won't be too very surprised at the price -- it's huge and heavy. And if you don't, but need it for a particular shoot, you can always rent.