Leanpub co-founder here. We're really happy with our minimum price + suggested price strategy, and have no plans to change it.
When coupled with our sliders which clearly show the (very high, 90% minus 50 cents) royalties that are earned by the author(s), and with our free update distribution, we get a lot of benefits for our authors, including:
1. When there is a low or a free minimum price, readers who otherwise could not afford a book can get it legitimately. This can help build a community around the book. For example, https://leanpub.com/rprogramming has over 80,000 readers (free + paid), and while it has a free minimum price, it is also our top book by lifetime revenue.
2. Quite often, there is so much extra income earned by readers paying above the minimum price that it entirely offsets refunds. (We have a 45-day 100% refund policy.)
3. Because of the royalty transparency, variable pricing, 45-day refunds and the fact that readers are supporting authors by buying in-progress books, there's a very, very low amount of nastiness. I really like seeing author and reader email; quite often "I love Leanpub" is part of the sentiment, regardless of whatever issue is occurring. (We also sell completed books, but much of what Leanpub is based on is our writing workflow and our focus on selling in-progress books...)