Even then, you've got a MUCH higher supply than you would with a scavenging event. And, don't forget that the only thing it costs people is stam, which is free and given out in large bundles. On the other hand, gold is hard to come by - so basically, when people get items for relatively free, prices are going to drop regardless . Additionally, when the goal is to farm as many items as possible simply for the purpose of composing, I think it's a bad idea to limit the supply. For the items whose supply would be limited, I'd feel as if it was best to not even include them.
I meant that some of the really old ones can be spawn instantly, while some of the newer ones can have a set spawn of whatever every whatever. I think if you limit the number of spawns enough, the prices will not drop all that much.