A RC's worth usually has to do with the troops CS(range)/cost.
Cost does not seem to be determined by CS of the troops only.
Troops who have poor equipment and training can be quite worth the purchase if they are dirt cheap and their planned use justifies it. For example, in Enweil I remember that one of our most prized centres provided troops for 15 gold per 10 men, I believe.
I was personally wealthy enough to hire a looting unit of 110+ of our finest archers, but I was quite happy to have that RC around for others and just in case. We did a lot of looting, where numbers mattered more than CS/man.
