I'm just rather stumped that at some point in the development process, Donald and the Playtesters (good band name) had something along the lines of the following discussion: "Yeah, this Event is too powerful to cost $13, but I don't think it's powerful enough to cost $15."
My guess is the $14 cost is because it's $3 more than Colony, which is $3 more than Province, which is $3 more than Duchy and so on. So the Event is probably a source of VP, perhaps as simple as $14-> Take X VP chips, where X is some number. My guess is that the tough decision wasn't what the Event the should cost, but rather what number of VP was a fair number, keeping in mind that a deck that reliably hits $14 every turn could add points indefinitely without bring the game to an end.
Actually, this can't quite be it. You could have two opponents just going back and forth buying the event, with the game never coming to a conclusion. Maybe it's $14 -> Take X VP, trash a Victory Card from the supply, where the Victory card is either something you choose, or something predetermined like Province. So you're adding some number of VP (is 6 too few? is 10 too many?), a Province is removed, bringing the game closer to its end, but now you don't have a Province cluttering up your deck. This is my guess.