Bah, Crucial is just selling you the same RAM at 2 different prices. Heck, there's probably 4 or 5 different prices for the same stick of RAM. That's why you never buy Crucial RAM from the Crucial website. 😉
They use Dynamic Pricing, where they look at your cookies to determine how to price you. If you're a rich mofo that purchases and looks at lots of nice electronics stuff on the net, they'll charge you heaps. If you're poor, or a cheap person, who skimps on everything and doesn't seem like the type who would spend a penny more than he has to, then they'll still try to make you their customer by listing a cheaper price. Using this method, they have a better chance of getting you to leave with their product if you don't have a lot of money, and yet they overcharge rich folks who don't care if they're paying $10 more than a poorer person. It's not like you'll ever know anyway, right? You only usually see the one price they list for you.
Just clear your cookies, prevent cookies in your browser, go to Crucial.com, and Refresh/reload the page until you're sure that you are getting the lowest price they offer. The price should change each time you refresh.
Or go to OWC and don't get ripped.