Years ago I bought a 700TI takeoff from David Walter for around $100. It screwed right on to my 725, with near perfect headspace. Lapping the lugs brought it in perfectly at minimal. Total time, including lapping was about an hour, not counting re-bedding the barrel channel with Accraglas for better fit, factory bbl being a bit fatter. That may or may not be needed in replacing "identical" barrels. My labor was "free" to me, and I had the tools already. Would not be to you
The stamping on my 725 is somewhere down in the barrel channel, but IDGAF, the gun is MOA as is. But only with one bullet weight. Finicky! To get the stamping back up where it "belongs" would involve using a lathe (which I have, but not currently set up - it was at the time) to set the shoulder back, extending the threading or relief cut, and then the reamer and gauges.
2-3 hours or a bit more to do it "right" if there is any serious fitting to do is not unreasonable. And if he is worth his salt, he gave you an outside estimate. It's always nice to please a customer with a lesser bill.
Keep in mind there are also tools involved, - headspace gauges, reamer, barrel vises and wrenches, recoil lug holder, measuring instruments , lathe etc.
Those need to be amortized over time also.
