on newegg windows xp professional with service pack 2 is $147.00 but yet look on bestbuy.com its $300.00 w/o service pack 2 and the one on newegg says OEM and i trust newegg
It's like anything else, if you don't shop, you might end up paying too much.
I saw RAM on special in a well known computer store, and they were (even on special) twice as much as what my small computer store sells it for.