I think you're awesome for doing that. Given the fact that the medium to big companies KP and Paizo charge extra for PDF (and I get it, it's not just layout - a good PDF has good hyperlinking), I can't imagine how much they'd charge for an epub. And at that point...if they're already pushing to demiplane....
What would be awesome (but maybe a pipe dream?) would be if they could find some kind of middle-ground where the fans could make the epub (some CC or open source hybrid) and therefore it could be given for free to people who buy the PDF? I'm not a huge fan of companies profiting off free labor, but if they're not willing to do it on their own...
I don't know, this industry is full of all kinds of weird one-off examples that aren't industry-standards. Like Paizo giving away all the rules for PF2e and SF2e which means the system can be free on Foundry and if you want the nice art, then you pay Paizo money. Or in my case, I like the books are art in, and of, themselves. So I buy the books even though all the rules are free. But no one is doing that. Probably because Paizo's money is from APs instead of the rules? But how cool would it be if WoTC did that? And Kobold Press? And everyone else? Because, as I said above, I understand it costs money to create a foundry module. I don't expect WoTC or KP or any company to give me that for free. But if the rules were free, then the community cna make the module. And the publisher can still make money on Adventure Paths, and token art, and other add-ons.