I paid $2k for US/UK taxes when I moved to London. I had always done it myself up to that point, including freelance Schedule C work, I definitely knew my way around the US tax code.

But then I move to the UK which has a different tax year, with a lot of subtleties over where my money was physically located, and what kind of expenses I could claim, and it got crazy complicated crazy fast. Paying $2k probably saved me $10k/year.