This reminds me of a question I've had for the longest time (+): why is it that in the US wiring money between accounts is so expensive or difficult? Whole ecosystems of companies have sprung up (PayPal and Stripe come to mind, and apps such as TransferWise) to reduce the friction when the banks could easily set up a way cheaper system that would actually be better (privacy etc.) for the consumer. The EU seems to be…
I think that the nature of wire transfers makes them somewhat risky. The institutions facilitating the transfers assume some of that risk for their consumers. If a large some of money is moved from your account to someone else's, and you dispute the transfer, the institution sending the wire may have to refund you the money.
The cost of a single transfer offsets the risk of the aggregation of fraudulent transfers. This could be a calculation of volume, fraud rates, average amount transferred on that channel, etc.
This is all in addition to network costs as payment processors (third party inbetween financial institutions)
So, fees = portion of network cost + risk offset
Hope this sheds a little light.