i'm not sure how he molds these things but i'm going to make a few conjectures here. first, i'm going to assume that he's injection modeling them rather than printing because i'm not entirely sure how good printing is and because i'm more familiar with injection molding.
models are fucking expensive. at i guess i would say that any of the kingdomdeath models would be between 10k and 20k for a mold. you really get reamed on the prices of them and tend to get tied to one injector.
second, runs aren't that cheap. he makes what he's pretty damn sure is going to sell and then waits to see if there's still significant interest so he doesn't end up 5k worth of plastic sitting around that no one wants to buy.
if he's printing, which i think he may be, then i'd guess it's much cheaper for the mold and i have no clue about the printing.