That's thinking like a captolist. The final empire doesn't run that way.
It's a plantation economy, like the old South, but I don't see anything non-capitalistic about it; there are wages, there is a standardized currency, noble houses profit from the ventures they manage... In fact, I fail to see any evidence that it's not
a capitalist economy. It's not a completely free market by any stretch of the imaginatino, and it lacks the robust financial institutions that post-Enlightenment western economies have, but there's no evidence that competing producers don't compete in order to increase market share.
As evidenced by the TLR's choice locations he wants to be able to find allomancers. Making it so they're pewter dishes reveal thugs is sound thinking.
IIRC, TLR was pretty apathetic about finding allomancers. The nobility were supposed to violently prevent any offspring that wasn't of purely noble birth, thus in theory all Mistings or Mistborn were well-accounted for, making producing Allomantic pewter to find those who slip through a complete waste of resources. Furthermore, TLR never
so much as mentions a desire to find Allomancers. The Canton of Inquisition likes to promote Allomancers to prepare them to become Inquisitors themselves, but that's a completely internal process; the Cantons might use Allomantic pewter for their tableware for that purpose, but it would still be easier to just beat them all silly, force them to swallow a vial of metals, and then say "Burn it," and see what happens. No, flooding the market with specially prepared Allomantic pewter isn't really sound thinking, there are already mechanisms in place to account for the Allomancer population, and TLR has no reason to expend resources hunting out every single Misting that slips through them.
Allomantic metals were treated as absurdly common throughout the series. That suggests they are far from rare(atium and aluminum aside) Look at Spooks tin barrel. Or the pewter bags used for burning. If allomantic metals weren't common no alas could obtain them.
Absurdly common? You're dealing with Kelsier and his Crew, an extremely capable bunch of Allomancers with connections and reputation throughout the entire Luthadel underground. They had the Resources and the Influence to hire a Kandra, they can keep themselves constantly equipped with enough Allomantic metals, prepared by and obtained from metallurgists, to use whenever they needed, in whatever way they needed. The fact that they don't ever run into a metal shortage is not really evidence that the general population just walks around and picks up vials of metals at the grocery store. I don't think metals are difficult to get hold of for those with a bit of cash, but I think there's a wealth of justification to say that unless it's specifically made to be Allomantic, a metal is going to be too dirty to use without harm.