This is somewhat true... Using the standard and gold cards as a reference... Is the 0.5% difference for charging and 1% difference in spending more than the % lost in purchasing MNX? An educated hedge would look at the falling price of MNX and deem it safer to transfer in BTC. In the last 3 months, it would hold far more value than MNX.
Again, I see no strong pressure to buy MNX
You compare replenishment % for fiat and spending % for other cryptos, while spending % for fiat is same as for spending % for MNX.
E.g. for Gold card to replenish card with fiat it is 0.5% for spending it via POS terminals it is 0%, ATM withdrawal - 1%