Guess what fools? If you do that, people who find stuff are going to shut up when they find rare objects and take them to a free-market nation to sell, and then you won't have anything.
Actually the British system works pretty well for both the government and metal detectorists.
In many countries it is illegal to metal detect period. In England, they regulate it a bit allowing people to detect and keep what they find unless it is something of significant historic value. In that case the government buys the item(s) from the finder a negotiated fee in order to insure that the items stay in the country.
It's not a perfect system but I know many people who have detected in England and 99% of them like the system that is in place.