Exactly Earle, is it worth risking your family's health over $900? Whose family is at "risk" though, the buyer or the seller? That's where the whole thing has gotten backwards. If the buying family is that concerned about it, they can fork over the $900. They just know they have leverage on the seller and the seller will eat the cost to do it, so that's why they push for it. They don't even have to have an opinion on whether it is a real risk or not, it's free for them, so why not.
But I could guarantee you, if it was common practice for that cost to be on the buyer, you'd have at least a 50% reduction in systems installed. Because then the buyer would actually be forced to do the research and weigh the "risk" against the cost. But that would be bad business for those other entities involved in this transaction, so you have what we have today.
Just follow the money, health issues around the world are only a big deal if there is big money to be made off of them. I think you could legitimately argue long-term usage of cell phones is equally as dangerous as radon. But, that's a billion dollar industry, so the powers that be have determined we're not supposed to care about that.