Thanks - ballpark numbers are of course appreciated - like what would be a typical 1 or 2 day job, what will be a 1 week job etc. :)
Not a professional artist, and bad with giving ballpark figures... but I do some 3d modelling as a hobby (and to get exactly that "feeling" for how complex a model would be).
It depends A LOT on how much details you need, and how closely the model should match your specifications.
If all you need is a low poly human character, you don't care about facial features (any would do), you only need some kind of armour, and maybe ONE thing that is a little bit special (a monster arm), yet nothing too detailed (diablo -> isometric viewpoint, tiny characters on screen), I would guess most artist could create the character quite quickly.
They might be able to reuse parts from earlier projects, they don't need to go into too much details, and so on.
Of course, retopo might be more challenging for a lower poly character (as every polygon needs to count now), and rigging and animation could still be a lot of work, depending on your needs.
What you can expect in what time though will depend a lot on the artist, as is what he would charge you per hour. I guess the ballpark for a very modest low poly model without details and not many animations would be <500$.... could be as low as 250$, IDK. But certainly not the >2000$ I would expect for a moderately detailed AAA (non-character) model.
A highly detailed AAA character could take multiple experts in their field (concept artist, modeller, rigger, animator, texture artist, actor in case of MoCap) many months in combined manhours, which could easely add up to >10'000$ or WAY more....
Again, a lot depends on the details.... some of the Online arcade tanks sims currently popular got quite insane with their newer tank models.... 100k tris and more, fully articulated tracks with physical sagging of the tracks themselves, every tiny detail on the tank modelled. Everything built historically correct, sometimes just from documents, sometimes measured on real surviving tanks, sometimes even with photometry.
Even though most of the labour seems to be done by freelancers in low wage countries, you can expect these models to be very, very expensive (and time consuming to produce).
ESPECIALLY if you include EVERYTHING involved, which includes the "concept stage" (measuring or photometry, AND actually negotiating access to the tanks/documents), and the integration / testing stage (there are a TON of things that could and do go wrong with such complex models even during the import and setup in the actual game engine).
One potential way of "guessing" what artists expect for a single model is to check how much they charge per stock model, and see if you find the sales numbers. That might be completly off for a new artist, but an artist who has been around the block a few times most probably starts to get a feeling how much he can charge. On the other hand, stock art often does not sell like hot cakes, so if an expierienced artist sells something for 50$, and got 5-10 sales, he most probably spent about the time he expected to be paid 250-500$ if doing freelancing jobs on it.
(Of course, if you are looking for kinda bog standart characters without much details, and are on a budget, you might be better off buying stock art. Will be MUCH cheaper, as long as you are satisfied with the quality provided. Problem then is making the different bought assets fit together. No idea if you can find an artist to fix that for you, and if that would be cheaper than to comission low poly assets really).
Always keep in mind that with freelancers, you will also pay some overhead to what you would pay an employee. They have their own expenses that the employer would normally take care off, they need to factor in downtime without contracts, and having to do additional work to find contracts.
