ad_hoc
(they/them)
It's illogical. PCs will go adventuring anyway and magic items are only as special as the DM presents them and the players view them.
Actually, the design of 5e makes magic items special. A lot of work needs to be done by the DM to make them mundane again.
Magic items would certainly be sold, or traded. But they would be special events.
It might take the form of a special auction. Low level PCs could be hired as guards/investigators to keep it safe. High level PCs might need to secure an invitation.
A magic item may be given as a boon. It might even represent a title or land ownership.
Maybe there are rumours of someone who found a powerful magic item in their house and, being a poor peasant, want to unload it to become wealthy. They are secretive though because they don't want it stolen. Factions are racing against the clock to find out who they are and where it is.