I would disagree with "clever", but it certainly is currently expensive. The degree of expensive can fluctuate and could be influenced. It is not guaranteed to remain expensive, and a nation state like the US could control 51% of the hash rate if it wanted to, regardless of the expense, I think . . .
Ah, so not ownership of coins but computing power.
Yep, Bitcoin uses Proof of Work (computing power) for consensus, while some others like Ethereum use Proof of Stake (coin ownership).