When I spoke to Ron Smith last year, the cost of a rebore and rifling was almost exactly the same as the cost of a new barrel.
Downside was that you paid for the work, whether it worked out or not. If the barrel is of a steel that is clean cutting and it all works out, you're in like Flynn. If it has any hard spots, or is tough and does not want to be cooperative, you will need to buy a barrel plus pay for the rebore work that didn't.
Maybe someone else works cheaper, but he does not. Fair enough. I figured that the guaranteed results from a new barrel made more sense.
Cheers
Trev