Bingo extra ball cost

I have been playing around a lot of online bingos : 90 balls, 5x3 card, 30 ball pick, and up to 10 extra balls.
I'm trying to make one similar as an excercise, but I can't figure out how to find out the cost of the extra ball:

I think that it is based on the prize that the user can win with it, and on the number of balls left, but that's just my guessing,
and I can't finde mucho info around, as this aren't the most popular games around.

For the stand alone progressive, I would have made several runs to find out the HA, derivate a small % of it, and add to an incremental
pot. Is this ok?

thanks in advance!.

This should help you out:
https://wizardofodds.com/bingo/90number.html

The exact cost would depend on all the specific rules. However, as a general rule of thumb, the fair price for an extra ball, before any balls are drawn, is about equal to the bet itself.

Hi wizard.

sorry to bring back an old thread to life but i found this thread and no answer anywhere to this issue.

what i try to do when calculating the cost of the extra ball is getting the odds for the next ball (ie 1 ball out of 30 that left) multiply it by potential wins across the cards.

however doing that to all of the extra balls increases the total return.
i assume i need to take into consideration the prices and wins of previous extra balls and maybe also take the desired RTP into account but not sure how to go at it.

any hints for me?

Thanks!
sirwinallot