Talk:Maximum Mine

The Maximum Mine isn't available to me, so I can't explore the options... but if one already has a mini-mine on an island, and wants to have the maxi-mine and is caught by the "only one mine per island" limit, why on earth would one sell the mini-mine and purchase the maxi-mine, rather than upgrading the mini-mine? The only benefit I can see is that one would get back the selling price of the mini, in coins, but one would have to pay 20 extra diamonds. It doesn't seem to be a good strategy.