Well, a lot depends on your performance metrics and your playstyle. For example where I am, Valken paints are $5-15 less per case than Ultra Evil, however none of them mark like ultra evil which is a huge benefit in actually getting eliminations. And you could have a low-end paint be nearly free for a great price/performance ratio, and I still wouldn't buy it.
Personally I play pump and always buy the best paint I can, so no one will have that natural advantage on me, while I will enjoy the advantage on others. Advantage vs disadvantage can be looked at like 1 or 0, you either have it or you don't, and if you do have it, there is no objective way to measure how much cost that is worth.