Hey Schuyler,
There's no real scale. The most important factors to consider are stats and resists (which are all lumped together, since 9/10 times a high gen cu will have those) and whether it's trained or not. A cu that's 'maxed' out and is fully trained to 50 will easily be worth millions as the time investment and leveling scroll investment and breeding investment went into it was astronomic, while a generation 2-5 cu with average stats you can scale anywhere from 50k-1mill or so depending on ALL the factors.
It also depends on what you want the cu for, if you should be using an AFS instead, but that's a whole other discussion.
I have a bunch of CUs for sale of all ranges, PM me in game if you want to discuss.
~Alexandra
Edit: Something I forgot to add, is that seeing how Cu's are rarely sought after by the highest tier players, they are less bred and trained than their AFS counterparts, which might drive their price accordingly.
