Maxperson
Morkus from Orkus
I voted occasionally. Sometimes the party can find someone selling something or maybe even a few somethings, but those things will be randomly determined. There is no, "I want to go buy a Sword of Truth."
The reason for that is while the OP is correct that items stick around pretty much forever, in my game they aren't things you can mass produce or even that other wizards will just have the recipe for. Further, the things you have to acquire to make a magic item are themselves very rare and difficult/dangerous to get. The end result is that rather than there being staves of fire, there is probably only The Firestaff, made by the Archwizard Shazbot. Some items in the DMG may never have been made.
The reason for that is while the OP is correct that items stick around pretty much forever, in my game they aren't things you can mass produce or even that other wizards will just have the recipe for. Further, the things you have to acquire to make a magic item are themselves very rare and difficult/dangerous to get. The end result is that rather than there being staves of fire, there is probably only The Firestaff, made by the Archwizard Shazbot. Some items in the DMG may never have been made.