Is it permissible to take the merchant's full profit in exchange for extending credit, and what is the ruling on increasing the price in the case of credit?

It is permissible to sell recharge cards on credit for a price higher than their cash price, because it is permissible to sell recharge cards for more than their value, and because selling for immediate payment is not the same as selling on credit. Furthermore, increasing the price for deferred payment over the immediate payment price is permissible and not usury (riba), for time has a share in the price. Selling on credit or in installments differs from usury because the item sold here is a commodity, unlike usury where the increase is purely for the deferment.