The coins weren't worth $1, $1k, or $1m to those that found them once they had to turn them over. They were worth $0.
As the article said, the “Saddle Ridge Hoard” had a gold value of $2.5 million and $10 million of numismatic value to the government.
As for a "blob" of unrecognizable gold, you must never have dealt with gold "eggs" that are common in foreign countries but are also traded amongst U.S. gold merchants. They pay well for untraceable gold.
If they had been confiscated I suppose you might have a point. Except, the weren’t. The gubbmint said “Nope, not ours”.
Nobody pays well for a blob of metal that might (or might not) be gold. That isn’t how this works. That isn’t how any of this works.
They don’t want “untraceable” gold. They want recognizable gold of known quantity, purity, and fineness. Anything else is discounted heavily.
While I can agree it would be “nice” to find a large buried treasure and keep silent, in practice it is extremely difficult to pull off.