Can an Attacker Recoup the Attack Cost through Block Rewards Alone?

It is possible, but highly unlikely and not the primary goal. An attacker needs to maintain majority hashrate for a sustained period to ensure they find all blocks and receive the full block rewards.

However, the true profit comes from the double-spend of high-value transactions, not the standard block rewards. Block rewards merely offset a small portion of the hashrate rental cost, which is the main expense.