>TLDR: Amazon pays roughly 70% of retail price for books priced up to $9.99, and 35% for books $10 and over. Amazon is the only retailer that does this. Other retailers, I make somewhere around 65%-70% no matter the retail price. Everything follows from that math, but if you want the details read on.

Wow that's nuts.

Is that something that the EU's Digital Markets Act (DMA) could change (in Europe)?

I missed the “run your own mail server” kickstarter by a few short hours. If only Michael Lucas was selling physical books on the side…