Out of curiosity, what would market rate for a sysadmin run to order a snowball and sync 24TB of data to it, ensuring that it ends up properly in Deep Glacier?
Instead, I'd look at contract system administration labor. It'll probably set you back 100-150$/hr with minimums of 2h. However, sysads can catch problems, set up alerting, and fix structural issues before they turn into humongous problems.
It would be my recommendation to do more hours with onboarding a consultant and a full audit (not SOX or FedRAMP or the like - but to get you aware of what you're doing even if you weren't aware). From there, a plan can be made to keep you up and running with low/no impacts. And once the hard part's done, should insulate you from any oopses. And the monitoring will help catching them in the act in case there's a new type of oops.
I hope I answered you adequately :)
Given that I was pretty knowledgeable about most aspects of backing my data up to S3, it would have been pretty hard to predict where the possibility for error would have been. I can't imagine hiring someone for 2hr to come and check my work, since they really would have had to be there for the entire process.
It sounds like about 2-5 days of work to get someone to set all this up, but perhaps it's more like 1 day at a minimum. So somewhere between $800-4k for that. Later in our project we were running 5 S3 buckets with about 20 stakeholders uploading and downloading, so that could have easily been another 4 days of work.
$800 would have been two years of what we were planning to pay Amazon. $4-8k would have been a major big-ticket item for us (even though, of course, that's the bill we ended up stuck with.)
If I were to do it over again I don't think I'd be able to justify spending on a pro. I would definitely spend on someone to audit our expenses more carefully though.