A high-end computer is a racing car. And like a race car, it requires a little more care and attention than something designed to get you from there to here. It will give you better performance, but at a cost, both in terms of money and possibly time.
What is a "high-end PC?" The answer is a bit misleading. Sure, high-end computers will be expensive, but it's important to understand what you're paying for and what you shouldn't.
For a high-end PC, you're looking for a machine that will run all the latest games at all the highest graphics settings and continue to do so for some time, preferably years. This is what we call "future-proofing" and since most mid-range PCs will run most modern games just fine, future-proofing is really the only reason to go high-end.