No offense meant to your character, 007.
I did not intend "profiteer"'s negative connotations.
The Yamataian government and corporations trade via a prestige system. The government gives corporations access to the raw materials needed (mining rights, farm land, other corporation's products and services, etc.) in exchange for their products and services. The more your products and services are valued by the government, the more access to raw materials you get.
I'm guessing this is done so that Yamatai can keep very close tabs on what its corporations are up to, very much like a strict parent.
The KS is mostly used by the corporations and citizens. Corporations pay their employees services in KS. Citizens use the KS to pay for products and services.
Since the only product salvagers produce is, well, salvage, I don't think the government would want any of that.
Best to sell it and pay the government a tax.
Do the salvagers pay taxes to Yamatai or the local government? Isn't it obvious? Both, of course. I have to pay income tax to both Uncle Sam and Lady California. Such is life.
Of course, Yamatai might not ask for a tax, so the, um, "federal" tax rate might be 0.
Salvagers, like self-employed people in real life, should be responsible for keeping track of their income and paying the appropriate amount of tax. But really, SAINT is not gonna come after your character if he forgot to account for that coffee mug he salvaged.