I think the price ToW charges for the plug installation is very reasonable. The price they charge per dovetail, however, is very high for the amount of work involved. But if price is no object and you're worried about doing them, then by all means have them done by ToW's gunsmith.
I had them do all the dovetails on my first build, though the dovetail for the front sling lug was not in the correct position, so I got my first experience having to cut a dovetail on that build anyway. On the next build I had no dovetails cut by them.