How do all the payment providers (grabpay, favepay, liquid pay) and virtual cards (youtrip, revolut) actually make money?

EBay started, and to solve the problem of paying via the internet, PayPal was invented.

Paypal was spun off, being more valuable than eBay.

Taobao wanted to solve the problem of paying via the internet since most Chinese does not have a credit card, Alipay was invented. Now alipay (and its competitor- wechat pay) is very valuable.

Transaction fees (paid by merchants usually), even as a small percentage, can be very lucrative since there are so many transactions per day. Just look at VISA and MASTERCARD, they are huge companies earning only a few percent of each transaction.

Don't be mistaken by the free transactions offered by most payment systems now, eventually, when they are having great market volume and power, they will be asking merchants to pay per transaction.

Holding data of all these transactions, these data are valuable to provide insights to advertisers too.

Advertisement, marketing from other retailers that tap on this tech firm to increase their business revenue.