I can only speak for myself.
I have never stooped to buying any map which offered buried treasurer of any sort. Those I know who have, never had any luck.
I can say the same thing for old ghost town maps, no matter who offered or sold them. Some are so bad, that the real site of the ghost town is miles away! That's not all.
Nowadays, one has to be very careful not to dig at sites owned by the fed, whichever entity you wish to speak of. Of the few maps I've seen, none of them listed modern boundaries. Without them, you're better off with a DeLorme contour map with important milestones (silos, windmills, etc.) listed.
Save your money!