It always amazes me when things like this happen. If you look at the comments on this post you'll see people responding as if this a terrific new idea/frontier. Others respond with links to existing solutions as you did; Gumroad was my first thought, too.

And to me, this is one of the main benefits of hackernews. I don't know everything, I don't know everything available, so I take value from everyone adding the options they know about.