You have a point friend, some of these items are priceless and worth as much on historic and cultural levels as financial levels. I truly don't have an answer right now but I'm sure museums around the world would pay big $$$ to buy such incredible artefacts to preserve them and exhibit them.
So if tomorrow UK offers us market value of Kohninoor diamond , but not the diamond itself will any Indian accept it. I will not because Kohinoor is our heritage and no amount of money can replace it.
. I was in Juniors (School NCC) we had to fire the .22 during competition cos a lot of younger kids had a danger of shoulder injury by recoil of .303.