Bundling question

I’m just about to finish a 9 book series, and am wondering if I should bundle it and, if so, for what price.

I’m getting decent reads and sales on the series, and each book is about 12k words. The individual books are all $2.99.

Does anyone have any experience they can share with bundling slightly longer books, and what price I should set? Also whether I should bundle as three sets of three or a single set of nine.

Having researched, it seems like the going rate for short form erotica bundling is $1 per book plus 0.99, so the nine books would theoretically be $9.99. It feels a bit crazy to be selling $27 worth of books for only $10, though and I guess I’m having a bit of cognitive dissonance accepting it.

Any help/insights/advice would be much appreciated!

Edited to add: I’m exclusively on Amazon.