Actually you'd be surprised - weapons get lost via death (and server reset following death), or oozes and slimes, rust monsters etc.
Also there are ALWAYS new characters - not necessarily new players (though we get them too) so we get dry spells and then I get 12K of orders in 2 weeks... but thats mainly with the main smiths on the server being inactive.
However there are way too many steel crafters on the server. Dorin, Daev, myself, Toli, (another dwarf I cant remember), Ruxie (believe it or not) and the Vardo and several other shady PCs are into or close to Steel making levels... meaning that the money comes even slower.
Selling to NPC should still make a profit but its hard to balance between letting smiths make money back and having them farm money by crafting and nothing but crafting until they have insane bank balances.
Yoshinaka has 8K in the bank... thats it. He's owed 6.9K in assorted debts but when they will be paid is anyones guess (though I trust the players 100% that they will), so its no road to riches, it is nice to be able to occassionally make money without dungeoning.