Fyndhorn Elves, from 1995's Ice Age expansion, is neither incredibly powerful nor incredibly valuable - its original printing has never cost more than a few dollars, and mechanically identical cards exist and only see niche play
That being said, Ugins Labyrinth has quite the downside and very specific deck building restraints
Admittedly, this isn't as much of a hindrance as it may initially seem, as you'll likely be playing only one or two copies in your sideboard and won't often have multiples in your hand, much like Relic and Lantern
Of course, repeated activated abilities isn't the only way to spend your excess energy
Based on the latest market prices tracked on TCG Stacked, Greenwheel Liberator is worth about $0.10 USD for a regular copy and $0.20 USD for a foil copy
Its basically free to cast most of the time, which makes it a cheaper Blackblade Reforged and it get to 10 damage way quicker