The proper industrial stuff can be quite expensive for sure. IIRC I paid around $400 per motor in total. You might be able to get a better deal on used motors/d

The proper industrial stuff can be quite expensive for sure. IIRC I paid around $400 per motor in total. You might be able to get a better deal on used motors/drives though. But steppers won't necessarily save you either, because that torque specification only applies to full steps. Harmonic drives are great but unfortunately quite expensive. What you might want to do is go cheap on most of the components and add a decent-ish encoder and use software to compensate for the imprecision. CUI's AMT series of encoders is widely available and comes with up to 14-bit resolution. I believe this can be a pain in the arse to get right but it sounds like you're comfortable with maths so it might work well for you.