Market value is $25, and seems fairly stable right now as well, albeit the foil version fetches 10x that, with listings up to $250 at TCGPlayer right now
It's especially great for Pokemon Cards for any fans who played the original games on the Nintendo handheld console
If they dont try to ramp their lands or simply get a slow start, this card might sit in your hand gathering dust, or you might have to play it to free up space in your hand before it can be used in response to a ramp effect or fetchland
Swans of Bryn Argol are highly unusual and crop up mostly as a way to draw cards rather than as a threat however it ends up winning a reasonable number of games simply by being a fairly big evasive monster that is hard to stop
They may or may not be the most powerful, because flavor matters
Assuming this is serious: "Why am I expected to purchase this product?" You are not