Usually more than you can sell it for....
If it is really worn inside, and most of them are... lots of them don't lock up well from wear. You can see when you close the action on an empty chamber and pull the trigger... when the hammer falls the breech bolt jumps up at the rear considerably and on inspection you can feel a "lip" that has pounded back in the receiver where the breech bolt locks up. Another is to slowly close the action while holding the trigger in the fired position and seeing at what point the hammer actually is released. It isn't supposed to fire until the breech bolt is fully locked up in place.... lots of them will release the hammer when the breech bolt is not locked up, sometimes when only half way closed.
If there are rust pits, it will not look very good unless you spend a lot of time in preparing the metal.
If there are no pits and it is just worn I don't think you can get a good polish and blueing job for less than $250. It should be more like $300 and up.
If you just want it sand blasted and blued it would still be $250.
If you disassemble and prepare everything for blueing and reassemble it after blueing it would only cost you $100... but you must live with how it looks and works......
How good the blueing looks is entirely in the preparation of the metal.