I've never had a lot of money, but I have paid attention to what works and what doesn't and how cost effective things can be. We used to make bows out of saplings when we were kids. They would last a day and we'd make a new one. Good enough for rabbits and playing around. A friend/mentor gave me a crossbow a couple of years ago. It's a killer instinct 355. It's a great bow. Killed a pile of deer with it. I don't see the need to go faster, but I don't shame the guys who want to. I have shot a 400+ model and it was nice, but they seem to have some durability problems above 400. Limbs break, strings wear out, etc... 400+ is a tall order for a bow. That string has to move as fast as the arrow and then come to a very abrupt stop. The string also stops the limbs, and that is no small feat. The cams, pins, and bushings take a beating. It has to be perfectly tuned to last more than 100 shots. The cheaper models are not always as smooth or as tuned as the more expensive ones, but it works the other way too. Sometimes you are just paying for a name or the speed, just like other things.
I can get a lot done with the money they want for some of those bows. 200 fps kills deer as well as 500 if you put it in the right place.