Yeah. I don't think its real practical to try to model a real system. On the other hand. No **player** needs 500 spoons, in the first place. A city *might* need spoons all the time. Trying to sell 500 of them to a village, where the *presumed* size is 20-30 people, is going to saturate it so fast no one can sell spoons to them for years. 500 spoons, in a city of 2,000-3,000 people on the other hand... But if everyone is making 500 spoons, its still going to saturate the market. Real merchants are not going to specialize, are going to sit on their stock till needed, while selling something else, etc. A real blacksmith, jeweler, etc., is going to do *the same thing*, tracking what is needed on the market, and only providing what the merchants/brokers need at the time. Big items, like magic cloaks, are going to **rare** production items. They will take time, be hard to produce, and more to the point, not produce a constant income, even if they do make you more in general in one use.
As I see it, the only way to "successfully" set up anything close to a real economy is to consider how big your city/town/village is supposed to be, figure how much they are actually going to need, put the players in competition *with* the locals to get the items, and maybe set up some sort of seasonal shifts, and fads. For 1-2 RL months the entire city might be making you huge amounts of cash from ear muffs, even in summer, then the fad goes away and someone else discovers that their entire stock of purple socks are selling out. Fact is, trade systems usually *don't* bother even trying to do this, so someone can craft 5,000 Gnomish Parachutes, sell them all off to the local merchant, and the merchant won't even refuse them. In a *real* economy, if some merchant buys that many in 2-3 days, you better start considering **why** and maybe set up your own stand in the market for them. lol
I don't think its necesarrily impossible to manage a good system, but it would need to work in a way that takes into account what *should be* possible, not just how far away the merchant is compared to the rest. Some players might just have to get a real job.
