The Ecclesiarchy won't send a fleet out to verify a box claiming to contain a shirt once owned by a saint.
That seems like exactly the kind of thing the Ecclesiarchy would send a ship out for. Not for, like, a street vendor, but anything above that? Seems reasonable.
The guardsmen who have such gear are few and far between in the lore.
They really, really aren't. It's not standard issue, but when your garden variety IG captain/major/colonel has one...an STC it's not.
In Dark Heresy it's something like 2 years wages for a well paid labourer to buy a shoddy one, and those two years wages only barely cover food and housing as it is. Not to mention finding someone with one for sale is nearly impossible for the average guy with no contacts.
Yeah but we're talking about the value of plasma to NOT indentured workers. We're talking the value of it to guys flying starships light years and being responsible for a crew of 20,000 people. It takes me 3 years of wages buy a new car. That doesn't make my SINGLE Toyota Corolla worth serious cash to an exporter. (Btw I work in the used truck parts and car business, so I can very easily see the line between "small time schmoe who buys people's wrecked vehicles for salvage" and "guy who owns a multi-million dollar business and buys fleets of trucks at a time.")
I maintain the only people finds of that scope are of value to are small time intra-system local traders.
The Rogue Trader book pretty much makes this clear. Single things, solitary objects, are not worth the time unless they are so stupidly rare and old they pay for the whole trip themselves, just on notoriety and opportunity. Scrap and single finds, even of stuff like plasma-tech weaponary, are of value to single, limited scope traders, who at best are on the lower end of the totem pole in a trading conglomerate.