But here they are physically printing the book in high quality, that's clearly something that's expensive to do. How much does it actually cost Steam per game they sell? It can't be more than a cent. But here it is actually costing Blurb money to print the book to the quality required. It's not just profit.
Providing hosting of game assets for decades and bandwidth for updating it and tools for running it on Linux and hosting for multiplayer must cost a bit more than 1 cent.