Lenses with wide apertures usually have more glass whatever the focal length, don't they? I mentioned the Canon 200/1.8 as an extreme example. It was considered by Photodo to be the finest lens they ever tested. However, the same principle applies to very expensive shorter telephotos, such as the Canon 85/1.2. Their advantage lies in the fact that such lenses produce sharp results at wide apertures. I imagine that at F1.2, that 85mm lens would not be particularly sharp. But at F2.8 it would be significantly sharper than the 50/1.4 at F2.8, but not significantly sharper than the 50/1.4 at its sharpest aperture of F8 (or F6.3 whatever).
You might be surprised Ray. I'm on the Nikon side of the fence so I can't speak for Canon glass in terms of their exotics, but in every test I've done with my 200/2G AFS lens, it's sharper even at F/5.6 and F/8 than any other lens I currently own (and that includes the 50), and in my opinion sharper than *any* other Nikon lens I've used in the past 30 years, and that includes any of their micro lenses, any normal 50, or any of their mid tele's. It's the one lens that I own that is limited by the resolution of the body behind it, and of course, by diffraction. As well it should be, given the cost of these things.
I do believe that when you purchase an exotic, what you are buying besides wide open performance is also a level of quality control and manufacture that exceeds that of most every other lens - being the exotics are typically built slowly and carefully, one by one, in small batches, with a lot less compromise in terms of the cost of components, so in the end it adds up to stellar optical performance.
I don't know if there are lens rental places out where you are like here in the states, but if so, try renting one for a bit and give it a go. Even if you never intend to get such a beast, they (the exotics) are eye opening in terms of what can be done in terms of lens design when cost/size/weight limitations are not present to constrain the designer.