So many Different prices for Win 7 pro...

Many online stores are selling products that aren't allowed to be sold, e.g. MSDN keys. A common sign of this is when they don't supply the discs, or when the download link will expire in 24 hours.

System builder OEM copies are cheaper than retail, but can't be moved to another system and don't get support from MS. Theoretically you're not supposed to use them for your own computers, but this rule is pretty much ignored.

Cue large amounts of spam below.