You are correct in that those items disappear because "not enough purchases" is not a number. For the "official price" they show because 0 is a number. This is how it is set up and is not a bug. But I did speak with a programmer and they agree that the page number should decrease with the amount of priced items. However, just as a note, this is a lower priority as it does not prevent game play.
When they do get a chance to fix it up I will post and close this up. For now I will leave it open for the page number bug.
Dexter by ❤