Apple Pay Cash with AMEX has Cash Advance Fee

I decided to try out Apple Pay Cash to send money to friends who paid for a meal two times last month. Since I did not have a debit card that worked with Apple Pay, I decided to just use my AMEX and eat the 3% charge to use a credit card for the convenience of using Apple Pay Cash. Well, not only was I charged 3% on each charge (as I expected), but I was also charged a $5 "Cash Advance Fee" by AMEX for each charge. Then I was charged interest on the cash advance amount at the end of the month on my statement. This means for paying for a $18 meal, I was charge $18 + $0.54 (3% fee) + $5.00 + .77% monthly interest = $23.68. Is this normal? Did anyone else have a similar experience with AMEX? How about other credit card providers, such as VISA?

Guess I won't be using Apple Pay Cash unless I can get a debit card that works... So sad.