We appreciate these questions and are flattered that you trust us with your buying/selling decisions! However, we are not a retailer. The best thing to do, is the following:
For new items, measure the prices between three reputable retailers. Tech is very competitive and retailers do everything in their power to keep prices low. For a start, compare these three: Apple, Tekserve, B&H
For used, this is tough. You have to be very careful when purchasing used. It’s not like an instrument where you can look, play and listen to it. Just make sure the seller is willing to backup their sale with some sort of Guarantee. As far as the price, the best resource is to follow ebay auctions.