Just played a game with
Changeling, maybe for the first time. It never actually got bought, but made me realize... what's the point of the on-gain ability? It seems like it would only be useful in somewhat rare edge-cases... The vast majority of the time that you are gaining a card costing
or more, it is because you bought it, or because you got to "gain a card costing up to X". In either of those cases though, you could have just gained Changeling directly instead.
So it seems like there are only 2 situations when you would actually use that ability... when there is another card that has an on-buy or on-gain ability that you want, but you actually want Changeling. Or, when you play something that allows you to gain an action, treasure, or victory card specifically; and you would rather have a Changeling.
Are these situations common enough to warrant what amounts to more than half the text on the card? Or is it just that it's very late, and after playing a bunch of games of Dominion in a row after having not played for a while, which is causing me to miss something obvious?