To 11's point above which DSatz has commented on numerous times, factory specs and thus factory matching can only be ensured for some random period of time after Schoeps validation anyway, so I don't think a used set of capsules that have matching certs, assuming the certs have not been validated recently is worth much more the paper the certs are printed on. Otherwise, some people feel it's nice to have a pair of caps with very close or sequential S/Ns so you might be willing to pay something extra for that.
But what does matching do for you when the caps are fresh from the factory? My contention is that, unless you're a studio, I'm not even willing to pay an extra $50 for matching if I'm using them for live music recording. Why?
a) WRT senstivity -- If I buy two capsules and they're either new or supposedly nearly new and they come to me very far off in senstivity, I'm sending one or both back and requesting a replacement, since one or the other is likely out of spec. In other words, the certs don't do anything positive or negative for me WRT warranting sensitivity matching...they're either close or they aren't, and if they aren't I'm rejecting the purchase regardless of what the certs say.
b) WRT Frequency Response -- If the two capsules don't track each other all that well, the effect is a shifting of the instruments of different frequencies in the stereo sound stage from what you'd hear on a matched pair. Do I really care about that in a live recording? Some people might, but I don't, especially since there's likely already a shifting of the instuments in the soundstage anyway from reality even on a perfectly matched pair.
Course, none of the above considers a bottom line reason why you might want to spend $50 for matching certs, which is simply to enhance resale if you ever decide to sell since some people insist on buying matched pairs, though IMHO having certs is nice but doesn't increase the value of a pair of used capsules.