How long is a piece of string?
Depends on who’s doing it, how bad the bike is, what kind of paint or powder coat, two colors? Lug lining? Structural frame repair? Location of the shop, quality of the work...
I can almost guarantee you’d be able to find a minty frame for way less. Restoration is something you do because you enjoy the process, it almost never makes financial sense.
It IS a GRAND way to learn tools and bike ins and outs and pride of ownership.