While Warframe is a perfect example of a well done FTP model, you can buy a lot of stuff with real money in Warframe, it isn’t just cosmetics. But it has limited PVP and the community is fairly friendly, so it isn’t so much Pay-To-Win as it is Pay-To-Not-Work-Hard.
This is very much a case of “When the rich play games, it is the poor that lose”. There is no positive outcome from this, regardless of what side of this story you are on.