It takes on average 2^54 hashes to discover a block at the current difficulty. So 2^48 attempts is 2^-6 (1.5%) of a block on average. A block is currently worth

It takes on average 2^54 hashes to discover a block at the current difficulty. So 2^48 attempts is 2^-6 (1.5%) of a block on average. A block is currently worth ~$2000, so 1.5% of that is ~$30