really set prices? way to start a black market, you think a set price would solve the undercutting?? no it would just drive it underground lol.
The only way to incress demand for things is to make them harder to aquire, take nether matirial, hard to get higer price,
So what happens if only farmers can harvest food?? well you would see the price of food go up,
what about if smiths were the only ppl able to create iron tools and aromor, Demand and prices would, go up,
What about if miners were the only profession able to mine diamonds, Prices would rise with demand,
Merchants would have to negotiate with miners smiths farmers and all other professions on supply and and it would add more value to the profession personally the only thing a merchant can do that others cant is sell stuff while there off line
I'm in NO way saying the above should be done, just saying that would be one way of pushing up prices, Look at the price of enchanted pics high demand price to match.. or iron ore compared to smelted iron,
Set pricing isn't the solution, limiting supply is, limit the supply and you have a more steady market place. I'm sure it would be an impossible thing to balance out between all classes but it could be done i would imagine