I asked my Facebook circle a similar question a year or so ago, when a grant I was being written into asked what my rate was for fly IDs (pinned specimens). I’ll summarize and elaborate some of what we discussed there.
For context, as a grad student I did a few small ID jobs pro bono for random folks as a way to get experience and build goodwill. I still do some like that, and I spend way too much time identifying photos of robber flies here on iNat, Bugguide, Facebook groups, etc, which I justify as a) outreach, b) useful experience, and c) it’s probably a more productive form of playtime than normal social media. Whenever I visit a museum for one of my projects I always make a point of reserving the last hour to do triage identifications from their unID drawers, as a small way of paying them back for accommodating me by giving them the most valuable thing I can offer. But now that I’m “an expert” and a “busy professor”, I feel like I probably ought to charge something for a bigger projects. Especially since I don’t have an extension component to my real job-- I’m pure teaching. I’ve seen that a few state extension offices (UC Riverside, Cornell, etc) have regular fee schedules for IDs posted on their museum websites, usually starting at ~$25/hour and getting more expensive for commercial or rush jobs. I know how strapped museums are for funding usually, and I’m not trying to bleed them dry. But I do want to respect my time and if someone asks for my rate I figure they’re prepared to pay something.
Anyway, for my grant in the end they offered $2/specimen and I didn’t haggle. A few other biologists on my thread mentioned seeing rates of ~$15-100 /hour for similar techincian / consultant jobs.
FYI all of the non-biologists who spoke up in the thread were blown away that we biologists sell our expertise so cheaply. Legal and finance types said things like “we hire academics all the time in the form of expert witnesseses. I don’t think I’ve seen anything below about $200/hr and I’ve seen over $500/hr for certain specialities. I think for someone with a doctorate, $20/hr sounds insulting.”
So yes, many biologists do IDs for fun and for free, and the culture supporting that norm keeps our market rates low. But remember that the “do it for free” mentality probably derives from the legacy left by old taxonomic experts who tended to be relatively rich privileged gentlemen who could afford to pursue their passion purely out of amateur love and not for a contract. Darwin could be Darwin partly because he came from old money.