I'm imagining the next scenario. I go to shop to get a TV. Considering that I will pay with crypterium app, the price of TV is 400€. I have a certain ammount of crypto that should be 400€ + 0.5% CRPT of that sum. I try to pay and have insuficient funs, I have only equivalent of 380€ at the moment of paying. I will tell the seller to wait a bit, because the price will increase in a few moments and will have enough funds to buy it.