Salam.
American Express (Amex) has a Gold Card for which there are a number of benefits, however, a £140 annual fee.
The understanding for this is simply;
"Credit card annual fees are a cost that your credit card provider automatically charges to your account to allow you to keep the card account open. They are a common credit card fee.
“Annual fees are the amount you pay for the benefits that come with your credit card. Not all credit cards have these fees. Generally, the higher the annual fee, the more benefits the credit card provides.”
Assuming that you aren’t paying the fee for cashback rewards but rather for the bonuses for spending X thousands of points per year. For me personally this type of card has been beneficial in paying for work/travel expenses as hotels/travel etc. would sometimes be hundreds or thousands pounds per week. You also get more rewards by being in this Gold category card member which leave you better off financially. Being in this category also gets you better deals with merchants/their partners.
Is this permissible?