We're inviting out-of towners to the evening only.
I have an aunty, uncle and cousins who live far away and don't see often (once in the last few years, at a funeral!). They expect an invite, but I'm not bumping close friends out for them!
H2B also has friends that he would like to attend, but again, doesn't want to bump out closer friends. Our day part is already bigger and more expensive than we wanted!
If there are a few coming, it's not like they will only be attending the wedding, they can probably catch up with other people over the weekend - maybe you can arrange to do something with them the next day as well?
If you're concerned, just pop them a message and say that as much as you would love to have them there for the whole thing, the budget doesn't allow for that, but you hope they can make the evening, and enjoy the chance to catch up with each other. I'm sure they will understand, especially if any of them are married!
Good luck! X