GMI is terrible though.
Sometimes you can see 6+ of the same item, all similar in price and a week later they are all still there, and so if i contact one of those sellers with a lower price they flatout refuse because its the "going rate".
One thing GMI is good for is looking at the buy orders, occasionally there are some serious offers on an item and you can ask the seller to go half way between the sell order price and buy order price.