My watch wrist strap is broken

How much would it cost. And should repair would be more economical?

It would be nice to know what kind of watch and strap you are referring to. Is it leather, rubber, canvas etc...?

You could go the OEM route, that would reveal costly; else, there are plenty of decent after market offerings out there.

An option would also be getting a custom made strap.

It all depends (again), on what you have in mind, and the allocated financial resources.