Ya the mercury contributes to the cheapness but it's also a very mountainous region with no nearby industry, tourism, or university. Both of those cheapen it to a point where you get more crime and worse education, all leading to the price you see today.

Many mountain towns have insane valuations and are not near a university, and many have high radon levels. I think it really comes down to it isn't valuable because no one else thinks it is.

That's why I said it doesn't have tourism. Clearlake area is lower elevation mountains that get no snow for winter tourism like skiing. That makes it a very different atmosphere than Lake Tahoe for good reason. One drive around each lake will very much tell you it's not about "no one else thinks it is." But there is truth in small starting differences being catalysts for positive feedback loop. What starts out a small difference can lead to wealthier people inhabiting the area, becomes even nicer, becomes even wealthier, and vice versa.

Heavy metal poisoning is only going to drive up the crime too.

And 80 acres for $400k doesn’t even sound cheap

But yeah lots of gotchas when buying land. Floods, fires etc.