It's a simple question. Some people are willing to pay for things they want in WoT, and others are vehemently against it. Do you buy things in-game?
I spent a lot of money for in-game content for various games (League of Legends, Hearthstone and so on) but I never felt the need to drop some cash of WoT. I don't know, I think I didn't "get close" enough to the game.
I've tried not to invest in it because it seems as if I'll just be even more hooked on it. When you put money into the game you're bound to invest more time. It's a fun game don't get me wrong, but I don't think you need to invest to make it any better. People at the upper levels pretty much give up for what I hear, so there is less of an incentive.
Generally if the game is F2P yes I buy some stuff but nothing really too expensive while I previously bought the game or it is ubscription based I tend to do not buy anything else from the market.