I would hit t6 worlds at this time when you use them if you can as their resources are much better usually for the higher end resources such as titanium and gems once you know their areas.
Otherwise it depends on the tools you get and what their bonus’s are.
I know there are a few like here that sell them for decent pricesfor the 3x3 aoe hammers: The Forgemasters Mining Team - commentary on a post bomb mining universes
Just make sure you check their extra stats before buying them so you pick the correct aoe tools and prices may vary based on sellers again as the forge tool market is very much in flux since the recent bomb mine nerf so it can vary from 15k for the 3x3 titanium hammers to 30k+ in other places or for gem tools.