Wow, glad I'm not around with you being in such a "chopping it all off" mood, lol!
I think the upgarde from 7 to 8 will be the smae , more or less, than from 6 to 7, it won't add the cost from 7 to 7.5+ 7.5 to 8, at least this is how I read it.
Most of the 7.5 features will also make it to the free 7.4, according to the Vue7 feature list available at e-on's, so I don't think many non pro users will upgrade if they don't have a maintenance plan.

"I can buy Carrara 7 Pro for about $380 'cause I have platinum club, for a comparison."
Sure, but what for? -)