I'm just wondering what that would look like. It seems a Sisyphean task at best, like seeking a needle in a haystack. And how do you make sure you don't accidentally damage a hard drive with an excavator? What makes him think the hard drive is not already damaged because it has been driven over or just the weight of garbage crushing it? What if his hard drive went through one of those conveyor belts with a giant magnet above it to separate metals?
I'm not an expert, but if you take the cost of the excavation project (not just excavation, but also sifting!), then multiply it by the chance of success, it feels like the expected value is less than the wallet.
It's interesting to think about though. You can easily throw away a pile of cash, but never half a billion. The volume would be too big, you would notice. But a bitcoin wallet of the same street value fits on a micro SD, it could literally fall through a hole in your pocket.