Here's why 10.x -> 10.2 upgrade is way too expensive.
When I upgraded from 9.x to 10.1, I paid approx 100UKP for an OS which provided:
1) Orders of magnitude more stability
2) A real multi-user security model
3) The capability to run web tools like Apache, Zope, Perl, Python, MySQL, PHP and ImageMagick
4) The capability to run SAMBA, tying my home network together
5) The capability to run essential productivity and mail tools like fetchmail, procmail (particularly to filter spam and make the Mail.App upgrade redundant), ssh (and hence pine and BitchX remotely)
6) iApps (especially iPhoto)
This was a worthwhile deal. It gave me the first opportunity to have the Dreamteam: the power and stability of Unix married with a highly usable and attractive GUI.
Now, the proposal is to charge me the same amount for a much more lightweight upgrade. I don't see how it's worth it for OSX.x users.