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