In a sibling comment I mentioned. If they do professional typsetting, around 3000 is not crazy. If I do the typesetting, then ≤500 is what I would expect.
Roughly how long does it take to typeset a 5 page manuscript?
If you go for high quality and work on the figures is performed, my (unreliable) guess is half a day for a professional designer. It takes me much more, because my latex skills are limited and because I insist on using the most standard and reproducible tools/packages in latex.
Haha, can I get a few thousand dollars for typesetting my paper? That's absurd. Sure you can spend a month setting it in your printing press or illustrator or whatever, but just using the journal's template along with LaTeX is perfectly good nowadays, and the hardest part is getting to it to compile.
Just using the journal template and looking only for compilation errors does not produce particularly good results. If I am preparing something for a journal like Quantum, where I am in charge of typesetting my work, it would take me a day or so to ensure figures are well placed and margins are not weird (in other words, not simply make it compile, but make it compile without warnings (not errors)). Most scientists do not care about the warnings latex emits as long as it compiles, and the results are ugly papers. I find it reasonable to pay $1000 to someone to take care of that processing (if they do a good job at it, which APS's and Nature's journals do).