My 10-year was 4 years ago, I didn't go.
I wanted to - really did, and my parents live driving distance from there, so getting back to town and having a place to stay would not have been a problem.
The problem was when the "leaders" - same class president, etc, that took charge of organizing the reunion, decided to hire a buddy's company to "host" the event, light catering, etc. So instead of $25-50 per ticket to cover the venue and DJ, it ballooned to $175 per ticket that included 1(!!) glass of champagne and some hors d'ouvres (I'd need to eat dinner beforehand), and provided a cash(!!) bar onsite. So getting a decent buzz going with my taste in fine whiskey, + uber ride there and back would set me back $300 to attend the event. Plus $~300 in plane tickets (ok, I'd get to see my parents yet again, but still!!)
This wasn't a snooty new-england prep school reunion, it was a high school in the suburbs of Sacramento, CA.