I did not buy it so far (for 20$), and if they give it away, they give it away. If they don't want people to pay 0,01 cents, they should put a minimum price of 5$. "Can't afford it" is just a rephrasing of "it is not worth more to me" in that context (I don't think anybody really had not spare $ in that experiment).

Personally I'd prefer them to have an option to give them money after trying the game.

Actually I ended up not buying it (and I was leaning towards 4$), because the PayPal form was too much of a hassle/couldn't get it working. Also I felt a bit like fooling myself - so far I did not buy it, now suddenly I am prepared to spent money? I felt I was falling into a kind of psychological trap...

I seem to remember that an address alone is already worth > 5$, so paying 0,01 cents is actually paying 5$.