Hello Damonlee
Yes I know the difference in price is astounding. I just bought and installed a 2 GB kit in my iMac which I got from Other World Computing (OWC). I ordered it from them on Wednesday last week and got it on Friday, total cost was about $58 including shipping. The new memory upgrade performs like a champ. I had priced Apple's at $300 for the same upgrade, just as you found. Had I not gotten memory upgrades from OWC for other Macs I've owned over the years and had no problems with them I would have been suspicious of the price difference. However, the old saying "if it's too good to be true, it probably isn't" doesn't hold here. Both Crucial and OWC have stellar reputations and stand behind their merchandise. I had no qualms at all ordering from them and am very pleased with the result.
My recommendation to you is as long as you get your upgrade from either Crucial or OWC, don't let the price difference worry you. It'll be fine and you can use the $250 or so you'll save for other things . . . including other Mac stuff both companies offer.
Here's OWCs address:
http://eshop.macsales.com/shop/memory/
Rick