Can someone tell me what the typical cost is to re-chase one side of a shell? And is that something most shops can do? Or do I need to find a frame builder?

I just found I broke my fixed cup (Drive side) - it sheared along the outer cup threads. I tried threading the cup back in and it feels a bit rough...I think it looks like it's screwing in cock-eyed, but hard to tell. A new cup might work fine, or I may have stripped the shell threads a bit (I rode it a few days with the fixed cup working its way out a couple of turns).

It's an old 501 reynolds steel frame, I was going to look for a bargain parts bin cup at the shop and failing that just pick up a cheap sealed Shimano BB. This is just an old 80s bike I use for commuting and street lock up so I want to keep costs down...