If there are no limits on the number of skaters, it would affect the competition scheduling, practice scheduling, and there would be additional expenses other than just the Zamboni driver.
The ISU had plenty of options to not blindside skaters like this though. They could just announce at the start of the season that there will be a number limitation as well as a minimum TES.
Even if they just made a mistake and forgot to raise the minimums or they didn't foresee that there would be too many entries, they could've been transparent about it and it would have been much less upsetting. This way, just feels like they're trying to squeeze out smaller feds. Whatever reason they had for doing this, they have handled it utterly unprofessionally.