What exactly effects trader prices?

I don't completely understand what causes the prices of the traders (dye, materials, etc.) to raise or lower. Is it a average representation of what the whole guild wars population is selling these specific items for, or what? Also what is the purpose of "request quote"?

Can someone please explain it to me in detail?

Thanks.

i think that it goes off the amount the traders have in their 'bag' compared to the amount that has been dropped. Its like supply and demand prices change in real markets

The request quote looks-up how much the thing your selling is worth at the moment

Prices, in general, rise and fall with supply and demand, but in the end the economy is controlled by A-net.

I could be wrong, but i thought it was simply "the more of a particular dye sold to the trader the lower the price becomes".

If dye X has not been traded in a while then prices of it increase, if everyone started to trade in their black or white dyes prices would fall substantially.

the more they have the cheaper they sell and lower they buy for. they have a specific number of everything, and its possible for the trader to run out of materials, dyes, or runes. "request quote" is to make sure they have that many in stock and it puts you at the current market price even if your trade window has been open for a day.

Supply and Demand, the market is set by the players for the most part.

Agree with that.

Although Anet can cause enough panic, to almost force ppl selling their stuff and lowering the prices.