They disabled NPC participation in the real economy. This gave way to the real player economy which took place in player-run shops built inside player-owned and customized housing.

Players didn't buy those 5000 junk skullcaps either. They wanted stuff that was actually valuable, which meant those practice items were recycled or thrown in the trash.

I remember when the UO team added trash barrels and created the "Clean up Brittania" event. The game's servers were struggling to deal with large numbers of these junk objects that people littered on the ground so the devs decided to enlist the players' help cleaning it up, just like a real-life public park cleanup project! Players got rewarded special items based on the amount of junk they cleaned up.