I agree with mahasamatman that the price of the ticket is only a small factor, and there's a point at which the price is really not important anymore. The price of C, IMHO, is useful only (a) in comparison to Y prices, and (b) to determine whether you'd rather use miles or pay money. Other than that, the actual price is kind of arbitrary.

I kind of look at it like all those late-night infomercials, where they throw in a bunch of useless garbage and tell you it's "a $150 value, FREE!" Who says it's a $150 value? If you add up the retail prices of all the individual items when sold separately (which they never are), then sure, you can get that number, but it's entirely arbitrary what that number actually is (especially in the case of infomercials). Yes, a C ticket might cost $10K, but that doesn't mean that I value it at $10K, similarly to mahasamatman.

It also depends on what your other priorities are. I might prefer to redeem for 2 Y tix instead of 1 C ticket, for example, so that I could travel more often or to more places... or, really, double that since I'd be traveling with my wife.