Glad the book can help! Regarding image size, it’s on my todo list now (see thread further down the page).

I am using Payhip for the transaction, and then Paypal. Fees end up averaging 0,5€. Calculating in terms of percentage is not really helpful here at such low prices: there is an incompressible flat rate pretty much anywhere you go. See it differently: these intermediary fees go towards making the UX smooth, the payment secure, reducing fraud etc. I want to spend my energy on the content, not making a credit card form :-)