What brand/model of regs?
I have a set of Apeks regs (DS4 plus 2 ATX50) that was due for service earlier this year. I was also looking at buying a set of used Apeks regs (DST and 2 XTX50), so I called my LDS to get a quote. They quoted $70 per kit plus $240 labour per set. So with taxes, over $500 per set. That price for the kits seems outrageous to me - especially for the kit for the 2nds which is nothing but some O-rings and one small plastic part. So I called 3 other shops (across the country) and got the same quoted price for the kits, some variety on labour, and variation on whether the service included things like the SPG or inflator hose connectors.
So, for Apeks regs, that's one data point. I'm betting kits for other makes/models might be cheaper - I'd be interested to hear.