I think USEF non-member fees run around $20 per show (or more). I showed at five USEF-rated shows this year. Not being a member would have cost more than just joining. And, they do offer a few services that make joining worth it. I like knowing that I have some type of insurance coverage. I don't know how good it is, but it's better than nothing.
Overall, it's easier to just give them the $55 bucks a year. I'm renewing, but it'll be a lot closer to the end of November when my current membership expires!