Comparing to the number one contender like Mac OS X, newest release--Leopard, Vista seems so expensive. But that's just a thing you automatically agree by the word of media without thinking by yourself. Just thing about it thoroughly, do we buy Leopard retail version or do we buy an upgrade version of Mac OS X? By comparing the method of Microsoft selling their OS, if you consider Leopard as a retail version of Mac OS, it sounds like you can buy an apple computer without an OS. That's the point of retail version. However, if you use one of Windows OS's family, you can buy an upgrade box with the same features as the retail one except the price which is almost at bargain price.
Take a look at the price of both company:-
Mac OS X Leopard Home version: $129
Mac OS X Leopard Premium version: $129
Mac OS X Leopard Business version: $129
Mac OS X Leopard Ultimate version: $129
Mac OS X Leopard 5-licenses: $199
I really love & hate this Jobs' joke at the same time. The fact is you can't buy a Mac without an OS, so, to be fair, all this version should consider as an upgrade when we want to compare with Microsoft's strategy. However, you could buy 1-license box around $100-$110 and $180 for 5-license box, if you just put enough effort on Google.
Vista Home Basic upgrade box $99.99
Vista Home Premium upgrade box $144.99
Vista Business upgrade box $189.99
Vista Ultimate upgrade box $249.99
and surely the cheapest one, OEM version:-
Vista Home Premium OEM DVD $111.99
Vista Ultimate OEM DVD $179.99 (both 32-bit and 64-bit)
Vista Home Premium 3-license OEM DVD $329.99 (both 32-bit and 64-bit)
You may think Microsoft is so suck to have so many versions, 4, of Windows, but that's just like a car. Not everyone wants to drive the fastest one like F1 or Ferrari which may consider as one of the most advanced engine and some just couldn't bare sitting on compact car like Yaris. I think if you want to most powerful one, just go for Ultimate and then you will find Home Premium is enough.
Oh sorry I'm out of topic a bit. If you see the price really, you will find that Vista price is not so pain comparing to Leopard. And you know that there still is a way to get this cheaper, like the way you pay less for Leopard. The thing Apple is definitely better than Microsoft is they offer 5-license package for a low price. (I think I could install 1-license Tiger DVD on many computers though) Nonetheless, I couldn't directly compare both Leopard & Vista because I don't know what version of Vista should be equal to Leopard; you may think the Ultimate one but Leopard doesn't have that much feature like Tablet-related features. Maybe Home premium is the one you could do that. So they are just not really differing from each other.
All in all, you know now both Microsoft and Apple are just the same. They both need money from us :-D ha ha ha
ps. OEM version is just the way to pay less, only a DVD and COA sticker you need. Otherwise is the same.