Actually - Vista Basic Home supports 64bit as well. All editions do except the (crippleware) Starter edition that only supports 32 bit and a whole lot of other limitations as well. Vista Ultimate (and Enterprise, I think) comes with both 32 and 64bit install DVD in the box, for Home Basic, Premium, and Business editions these only come with 32bit install DVD or CDs. You can however obtain the 64bit install disc from Microsoft on their site (for a few $ to cover shipping and cost of media, as I recall).

That price seems extremely low for any version of Vista, are you sure this correct? The Microsoft employee price is the lowest I know of (short of stealing) and it's around $25 for the cheapest up to $45 for Ultimate... I just helped a teacher friend of mine with upgrading her machine to Vista Home Premium and that cost $80 USD for the educational price retail box.