I agree with SaxonPig with possible exceptions.
Police trade-in's can be a way to get a solid shooter at a reasonable price, but a professional refinishing job can bring the total cost up to, or higher, then the price of the same gun in like-new condition.
The finish on a "to be used and carried" gun doesn't matter because in and of itself it has no affect on how the piece shoots. If I pay big-bucks to have it refinished I'll slowly lose my investment as I put my own wear & tear on it.
So what are the exceptions? Well if this is a carbon steel revolver I would consider a sand-blast and Parkerize finish, that is relatively inexpensive and can even be done by the gun owner. You end up with something that sort of looks like a World War Two Victory Model. The finish isn't pretty, but it is functional. The other exception is a stainless steel model, that can have the "looks" referbished with a little elbow grease.
Otherwise run the numbers before you lay any cash down.