Publishers really focus on first books in a series. They HATE having the “tail end.” So, yeah, if you have self-published books 1 & 2, getting them to publish 3 - n is even harder. Even if you had killer numbers for 1 & 2 they wouldn’t take that deal. What they would do (and again this is rare). They would have you remove the early books and they would republish the whole series under their imprint.
Your response makes me curious now. Going with the example that said book 1 and 2 have excellent sales. Are they rejecting book three because they would rather have control (appropriate rights, distribution, format etc) over the entire series as I assume they see triple book series as a single entity so to speak?
Or would it be they just don’t see the incentive to pick up book 3 and only receive a portion of profits when they could have had access to the entire cake?
Or none of the above.
It’s the FIRST book of the series that gets the most marketing support. Because when you are 2 - 3 books in you are already narrowed down to people who have read the books before it. Without control of the first book - where you can do things like discounts to get a flood of poeple in, you are significantly hamstrung.
It’s not about “having the whole cake” it’s about being in control of the bellwether (lead sheep). You can’t steer from the back… you need to control the front of the train.