I bought the family pack because (1) it is priced right; and (2) because Apple makes it easy for me to be honest!
But which of the six versions of Leopard should I buy? Oops-- I forgot-- I was thinking of that OTHER operating system.
Uhh...
"Leopard buyers has the same 30% family pack/70% single-user proportions John notes,"
is not a sound assumption. Gruber readers are much more likely to be major mac nerds then the average population. Those Daring Fireball types are the guys that have 4 macs each. Major nerds. The average of leopard sales can't be anywhere near Gruber's subgroup. I'd say his readers are 3 or 4 times as likely as average to have more then one mac in the household.
OSX upgrades should be free since OSX only runs on Apple computers. It is like upgrading the "firmware". It is not like Windows which is licensed to many OEMs, but Apple has tricked users into thinking along those lines.
Parallels and Fusion seem very popular. So how many Mac users install Windows? Do they buy it or pirate it?
Bootcamp is one step short of pre-installing Windows. So when is Apple going to sell pre-installed Windows?
"OSX upgrades should be free since OSX only runs on Apple computers."
Huh?
I think your analysis is conservative in that I think the number of families that would buy multiple copies for multiple macs in the absence of a Family Pack would be very close to zero.
The Family Pack really is genius, Apple style. Simple way to be fair and legal, reasonably priced, pure incremental profit.
There is another benefit to Apple's "trusting" approach. Even though Apple would like to get paid for every machine running Leopard, it is also in their interest for machines to get upgraded even if they don't get paid.
If Vista were a cheap and easy upgrade, it would be more prevalent, and that would help MS with the chicken-and-egg problem of slow 3rd party support.
btw, I have a 700 MHz machine that I would really love to upgrade (if performance lags a bit, fine, as long as iTunes' playback is still solid). I am looking forward to your report on how this goes.
I went for Leopard Ultimate. 
Hey beanie, wanna bet that more Windows users use pirated software? How much you wanna bet? Also, if you change the motherboard on any PC but keep every other component, you are not allowed to reinstall Windows legally. Feel free to call the mothership in Redmond to verify. You can switch the Mac OS to any one computer, or more for the family pack, which costs less than Vista Home Premium version.
There is a point that has been made obliquely several times, but let me restate it and push it through to a hopefully more interesting conclusion.
(1) There is no such thing as buying a New Installation of Mac OS.
(1a) Every box in the store is an upgrade, because it will only install on a Macintosh, which included a version of Mac OS in the original hardware price.
(1b) New versions of the OS are just bug fixes and other improvements to keep the customer base happy so someday they'll return to buy another Macintosh.
(2) Microsoft doesn't sell computers, so they have to make all their money just on the software.
(2a) So comparing the pricing structure of Windows and MacOS is like Oranges and Apples.
(3) BUT: Microsoft requires (when they can get away with it, which used to be all the time and is now merely usually) commercially created PCs to have Windows pre-installed, and they get paid for that.
(3a) The number of PCs made by hobbyists or otherwise without that constraint is a very small percentage. Forget about it.
(3b) So it is not as different as you thought. Microsoft essentially just contracts the Original Equipment Manufacturing to other companies. If they can't make a profit then perhaps their business model has expired.
Commenting by HaloScan
