I'm sorry, but what exactly are you paying for? You can't actually buy anything in league of legends to enhance climbing ability.. unless your going to pay $500 for some random to come and boost you a couple divisions which would do nothing because most people would just get demoted right after getting your account back.
Unless your stating that the more things you buy.... riot will somehow make it easier for you to climb which doesn't and wouldn't make sense in the slightest.
They would basically have to implement an AI to find the highest paying players and give them more LP/game which would be a complete waste of time.
They wouldn't benefit from doing that at all. I also doubt most people would even pay that much to climb ranked... its literally worth nothing.
If that was the case I don't think LOL would be the most played game in the world.