[Thanks to Steve W]Linde Waidhofer now runs with the interesting approach of "tip jar": giving her photo ebooks away for free, and let anybody pay what they think they were worth. I hope it's successful. I very much liked her Mexico book (pdf link) and I paid a tenner. (I seem to be a little tired of landscapes now. I think it's very hard to put your personal touch on landscape photos.)
I wonder if a tip jar can work well? Certainly photo books are not known traditionally for being gold mines, so it might be possible to beat that record, not the least for the lack of print costs.