As previously mentioned, you have to look at various sites because a site offering the best price on one item does not mean that same site is the best on all items all the time. I think, on occasion, dealers just want to get rid of stock.
I get the BMW part number (realoem.com) for the part I'm looking for, Google it, and look at the sites which come up. At times it's been a dealer in California, other times it's been a dealer in Connecticut advertising on e-bay.
Always check out shipping and taxes. Some will lower the item price then get you on shipping and handling.