Sounds more like wrongmove.co.uk to me.
The price of undeveloped and undevelopable hill land in Wales is something like ?1000 per acre not ?14,285 per acre, and this sale doesn't include the mineral rights, there's no planning permission, no obvious touristic parking, no buildings other than small ruins, and all the encumbrances of a disused mine and surface quarry.
On the plus side, the quarry has a terrific collection of old cars from, I guess, the 1960s onwards:
https://www.reddit.com/r/submechanophobia/comments/ha07pw/the_cavern_of_lost_souls_abandoned_gaerwen_slate/