Is it permissible to purchase an online shopping card for $40, sold for 171 Riyals, knowing that $40 equals 150 Riyals?

If the card contains a financial balance, then this balance takes the ruling of the currency in which it was stored. It is not permissible to purchase this card with the same type of currency stored in it, unless the price is equal to the balance contained within it, due to the condition of equality in quantity when exchanging. However, if it is purchased with a different currency, there is no harm in that, even if its price is higher than the known exchange rate in the market, but it is stipulated that the exchange (handing over) takes place in the same session. So, there is no harm in purchasing a card with a balance of 40 dollars for 170 riyals.