If Jewish books are sponsored why do I have to pay for them?

Every time I pick up any sort of sefer (Jewish book) I see that it is sponsored by someone. I understand the whole “sponsor in the name of” deal, but what’s the deal with the authors, do they get paid twice? Why should we have to pay for the book if it was sponsored?

I always feel like I should be getting something for free if it says sponsored.

Are secular books ever sponsored?

Anyone want to sponsor my upcoming book?