I do not like this idea BUT it could be changed just a bit
instead of having a brand new token u can get something maybe directly from shop?
but not everything, maybe items like food, blocks, and some sort of armory
Examples :
1 steak = 5 iron
1 steak = 3 gold
1 steak = 1 diamond
1 golden apple = 2 gold
1 golden apple = 1 diamond
So this is the rule i have, if you can normally buy it with iron you may buy it with both gold or diamond, if it is gold u cannot use iron but u may use diamond, if diamond you may only use diamond
as in which way would you like to pay?
but of course i think the general idea of yours is a very bad thing, because this will encourage campers (-1 point for me for lack of creativity in this reply), and if you somehow managed to trap a player to stick to their island with only an iron generator with time they could have = gear to yours and just removes the purpose of middle (or middle just speeds things up)