Best Price (White Giant)

I note that premium accounts are allowed to use more than "best price" as a strategy when selling items. Why would you ever want a situation besides best price, unless you had an emergency shortage? Is there some tactic I'm missing?

Best price mean you get the best price per quality but you ma y pay more than you want. For example if Something has market price of 1000 and 300 quality if someone offers it at 2800 and best price you will probly pay that. But if you set fixed price to 1200 and someone offers thier goods for that you'll pay that price rather than 2800 a saving in this example if 1600 per unit.