I found this part interesting: I also don’t have their permission to disclose the amount of the sale, but suffice to say that it was proportional to the amount

I found this part interesting: I also don’t have their permission to disclose the amount of the sale, but suffice to say that it was proportional to the amount of time and effort I’ve put into it (that is, not much). He clearly didn't build it to make money, but why would it be proportional to the amount of time and effort put in? This doesn't seem to me like the most important thing to consider when selling your work, unless it's a contract job ;)