Appears Transferwise just partnered with Facebook to allow transfers through FB Messenger. I've not used it yet but sounds like it could be a viable, cheaper alternative... http://money.cnn.com/2017/02/21/technology/transferwise-facebook-money-transfer/
Potentially, though wouldn't that require both parties to be friends with each other? Seems like that may be more trouble than it's worth.
I've used transferwise.com and its pretty good. I have no interest at all in doing so through Facebook, but I'm sure a lot of people will.