Disclaimer: I haven't made games, nor ever tried to sell games.
I like the pay-what-you-want (PWYW)* model for selling digital goods. It solves several practical and ethical problems associated with setting a single, world-wide price.
Free-to-play (F2P)** seems to improve upon that model: you pay as you go, or don't. You don't have to decide what the product is worth before you've tried it.
However, unless you consider your time worthless, you can't actually just pay what you want. In today's F2P games, the alternative to paying money is usually paying time. That comes with the punishment of breaking your flow. So, the minimum cost varies by person, but it is not zero.
Now, all I've said is that people might not like games that cost too much, but I used a model of cost that depends on what people dislike! That's useless. However, my point is that free-to-play could be a better form of pay-what-you-want, but to get there, we need to see how free-to-play isn't free.