IMO most 'customs' are a complete mess, and most don't shoot worth a **** -in any brand.Also, Remington 700 customs being a mess? Really? Trued by a competent smith is trued and squared, regardless of brand. So if it's built right, regardless of brand, it should be a shooter.
Of course a small percentage do turn out well, and there are a small percentage of builders who actually know how to DESIGN a good gun(not your design, but theirs), some can build them well also.
One of these is COOPER for sure. You pick one off the shelf at Cabelas, put a good scope on it, develop a load, and it WILL shoot well. If you also find off the shelf ammo that shoots well, it's value blooms a little more. Good investment.
When you take the term '700', you're basically talking about a pawnshop donor action, as it only comes down to this beginning point. That's what I see in classifieds(with the scope removed).
Why begin the investment while already knowing this core of it will need a lot of work by a 'competent smith' just to begin, and given all our choices today?
Well I suppose it could be fun if you're sentimental on Remington for some reason, but the end product will not actually be a Remington. It will be a bunch of parts screwed onto a donor action(another 'trued' action out there). That's it's value, and classifieds support that much with them.
Now if considering a great gunbuilder, like GAP, and they build on a 700, then that's easier to consider. But I wouldn't choose this. Actually, I wouldn't waste the space in my safe for it.
I would want a GAP with one of their templar actions, as this would be a lot more valuable, and knowing that makes the investment easier. This I would make room for.