The big issue I see is this... Your applying -real- world economic sense, to a -fantasy- race that is renowned in most mythologies for it's insatiable greed for gold, be it just the metal or jewelry made from it or big fat gold coins.
And you misunderstand something, economics is only in our western civilization about getting wealthy, in all other societies and times it is about survival.
Simple,
first decade of overproducting our uneconomic dwarfs can buy with their gold houses, clothing, food, axes, hammers and chain mail(ok, thats double counting), gold production increases, not by more dwarfs taking up the trade(because they all do it anyway), but by number of dwarfs increasing and they all dig.
Second decade of overproducting gold price slowly drops, our uneconomic dwarf continue to dig, but cannot buy clothing anymore(doesn't matter to them, chain mail is enough), production increases with more dwarfs existing.
Third decade of overproduction gold price slowly drops, dwarf continue to dig, but cannot buy axes anymore(hammers are ok for war), gold produced still increases.
Third decade ... cannot buy houses anymore...
Fourth decade ... cannot, after hard discussions, buy chain mail anymore ... production levels, since higher infant and youth mortality due to more crowded living.
Fifth decade ... cannot buy food anymore, production drops due to quite some dwarves starving, but they continue to dig and overproduce.
Sixth decade ... cannot buy hammers anymore, production drops dramatically due to missing tools and lot of dwarves dying from wounds acquired by crushing stones with hands.
Seventh decade, dwarves nearly extinct(except for the economic ones), no longer gold overproduction.
So, the uneconomic dwarves might continue to overproduce, but in the end economy will still get them and the overproduction will lead to low prices, which then leads in the long haul to a lowering of production.
This is BTW not only joking, but serious, communist in various places tried to enforce production in spite of economics and starvation happened often as a result.