I don't believe in the "diminishing returns", at least not as a universal truth. When you're in to the subjective the value of the return is up to the one who spent the money. That, and a $100k system does sound way better than a $20k system-assuming equal skill in gear selection.
No, I'm not saying that every economic step up gets positive results from every piece of gear. I'm saying you don't always get what you pay for, but you almost never get what you didn't pay for.