Yeah, I'd like a better explanation myself. I feel it, but I can't really explain why.
It seems like there are just two distinct modes. When you do something for free, you're basically doing a favor, and you get pleasure from being altruistic. Once you get paid, it's now an exchange of value, not altruism, so you only get pleasure from being paid. If the pay is small, you'll feel upset because your end of the bargain is based entirely on that, while if you're doing it for free, you switch over.
It seems like there are just two distinct modes. When you do something for free, you're basically doing a favor, and you get pleasure from being altruistic. Once you get paid, it's now an exchange of value, not altruism, so you only get pleasure from being paid. If the pay is small, you'll feel upset because your end of the bargain is based entirely on that, while if you're doing it for free, you switch over.
I could be full of it....