TF2 is the least odious f2p game in general. Nothing forces you to buy the keys. But the numbers show that simple psychology causes a lot of people to open them

TF2 is the least odious f2p game in general. Nothing forces you to buy the keys. But the numbers show that simple psychology causes a lot of people to open them just to see whats inside. F2P in general is based on the notion that 'if you give someone a reward for something, they will pay for more of that reward'. Alternatively, if you give someone a way to make it easier to "achieve" that reward, they will pay you to make it easier. So therefore f2p games are designed around getting you into essentially a skinner box where you get a constant rate of rewards and can either pay to make the reward process easier or you can pay to make it happen more often. The problem with this addiction model is that it puts an incredible amount of stress on your users. These games are not inherently fun, they are just addictive. The stress leads to burn out and players quitting. This is all on a spectrum of course, I would barely categorize TF2 as using this model. Zynga games define this model. Edit: let me tie my last 2 paragraphs to my first. In TF2, you can either get new guns at constant periodic intervals. Or you can pay to get them in crates, which drop fairly often. This is a skinner-box/addiction model. It is a small part of TF2, but Zynga games use this as the basis of their game's design. More and more games and using this model and fall somewhere in between Zynga and Valve. The problem is the slope towards Zynga is steep and its easy to make people buy things if you use Zyngaesque features. This benefits your company in the short term but kills it in the long term.