Average prices vary according to location. Depending condition you can expect to pay somewhere in the $300 - $400 dollar range.
IMO I would not consider reboring an SC, good one's are getting harder to find. I would buy a CS or C for a rebore project...more of them out there and cheaper to buy. If you like the look of the 1/2 mag on the SC (and who doesn't) you can shorten the mag tube when you do the rebore.
If you are in the market for a 444. It would be more cost effective just to buy a used one and call it a day. They already have the 1/2 mag tube and look similar to the SC. The 375win are harder to find and do command a premium.