Thats a good point. The dwarves obviously figured they had eons of time to build up a stash of say 500m GP so they wouldnt have bothered saving in the first couple of years. I can use that to explain why they don't have that lying around.
As for the army idea: Ofc the dwarven armies are...
Question speaks for itself but for some background:
Im creating a oneshot in which Mammon (Archfiend of greed) has tricked a dwarven lord into accepting a deal that reads: "your mines will have undepletable riches for 201 generations at the cost of 1% of the total wealth gathered + a fee of 1M...