The 750GT is the least expensive of the round cases, and they are still expensive. The worse scenario is to have and 860GT, the least desirable of the bevel twins. They aren't worth much (relatively) and cost as much to fix up as their vastly more expensive 900SS brethren because they share so many parts.
#dontaskmehowiknow
You might want to sit down after seeing the asking price on this bike:
http://www.bevelheaven.com/bikes4sale/BH-1972-750GT/index.htm
And no, your Commando didn't appreciate at the same rate.
#alsodontaskmehowiknow