I have had 2 professional fits. They were worth it.
My last one was a Retul fit. It took about 4 hours and I learned a lot about my position on the bike. It was like 5 years ago and I am pretty comfortable on my bike. I did find out that one leg is slightly shorter than the other and they needed to shim my left cleat with two shims. My first fit never caught that issue.
So, for me, it was well worth it. I've managed 3 centuries and a bunch of other metric's without any issues at all except for a bit of chaffing here and there.
john