Until time proves otherwise, based upon the history of "hot new ccTLD/gTLD launches/promos", I'd say it's a safe assumption that .Co owners exist in a .Co speculative bubble.
Remember, also, that we're on the frontier of possibly new, unlimited TLDs: .ca, cb, cc, cd, ce, cf, cg, . . .aa, .ab, ac, ad, ae, af.
I'd play very carefully with a .Co that might being trading off any brand or existing site. Not saying you are. Justsayin#. :P
Multiples or "products" (of division) as a domain value methodology? Big doubts there, but "if you can sell it (the idea)" then more power to you.
I wouldn't assign any multiple to a .Co.
I'd look at the root word (1 word only), how generic/commercial it is, volume/demand, . . all the usual signals of value.
Then I'd look at "registry risk" (Colombia? Ya, seems safe to me), who is promoting it (Lemme see . . oh yeah, Neustar . . didn't they promote . . ), search engine un-love due to the facile assumption that "if it's a keyword it will/must rank", and other unkind variables/assumptions.
I guess, by now, you've figured out that I haven't bought one, don't own one, and likely would decline one if offered as a gift . . Too bad it's not a tulip bulb frenzy. I'd take a few of them off your hands . . but, of course, everyone KNEW how valuable tulip bulbs were so no one would have been fool enough to give away their bulbs . . :-/
Sooo . . . sure . . if you can find a suc . . err . . buyer . . 1/10th to 1/20 of the .com value or sale price sounds about right.
:P :P :P :P