1971 Plymouth Duster Rotors and calipers

Should I buy a new hub any idea how much they go for?

Why do you need a new hub, if your replacing rotors?
Is one of your hubs buggered up for some reason or other?
Hubs are not available new.
Old hubs have to be found by advertising in "wanted" sections in every internet forum that you can think of.
They are pretty hard to find now-a-days.

As Doug 371, the above poster stated, you just press out the studs to remove the hub from the rotor.
There is no "cutting " involved.

If your machine shop is charging $60.00 to press off 2 rotors, and then press on 2 new rotors, your paying their shop professional labor rates to do that job for you.
Maybe it's high, but what are hourly labor rates going for, in your part of the world?