this has been discussed repeatedly, but at the endo of the day there is no comparison in quality and most importantly cost.
OH, yes there are those that say you you can spend less money and have an action that shoots very well, but it does not compare head to head with a custom and it will not be worth what you paid for it. That last part is absolutely undisputable!!
Trued 700s for sale bring no more than $450-500 absolutely tops, yet cost $750-1000 to get there when you include the cost of the action/resale value ($300)
To take a Rem 700 and truly blue print it, recut the threads add trued lug, change firing pin and springs and sleeve the bolt, etc etc where it is supposedly comparable to custom, it will cost you more than the custom action.
Most importantly the moment you pay the gunsmith bill and walk out it will only be worth about 50% of what you have in it.
Also it will not be as good an action as the custom. The customs normally have more accurate machining on all dimensions such as bolts, lugs, raceways, longer tenons, more accurate threads, better firing pins and holes, extractors etc. those are things that normally CANNOT be smithed into a Rem 700 locally.
Now if you are a smith and can do all the work yourself or someone will do it for an obscenely cheap cost, OK it is cheaper but it will never be equal much less better.
BH