When one side already holds a very extreme position, "reasonable compromise", to them, is likely to look like "I give up everything, you give up nothing/very little," because coming from an extreme position to a reasonable one is by its nature going to be a long trip.

I am fully aware that not all gun owners in America espouse positions as extreme as, "There should be no waiting periods, no background checks, and no restrictions based on mental health for buying any weapons up to and including truly military-grade hardware," but so far as I can tell, that is the position the NRA has taken in this. Going from there to anything that I would see as a "reasonable compromise" would definitely require the other side to give up quite a lot.

Personally, I own no guns, and am uninterested in them, so a 2nd amendment repeal, full ban, and confiscation would not have any direct negative effects on me (and I would not object to it). However, I would be perfectly comfortable with gun control that was far short of that.

To answer your question, though, in the end, what non-gun-owners "give up" in any compromise with gun owners is some safety. It's certainly an intangible, and there's no way to measure how much is being given up at any given time—it's possible, depending on the particular restrictions that are and aren't enacted, that they give up almost none...or a great deal. This is an inherent problem when the compromise in question is about restrictions on possession or use of a thing: people who do not need or want it, but see a reason that it should be restricted, are never going to have to give up something as easily quantifiable as those who do want it, no matter how objectively good the restrictions they want are.