They are also expensive. Usually $6 per transaction IIRC when I used to pay my rent.
With such an easy method of sending money between people, it's extremely handy. Compared to what I'm used to in Canada, only thing that comes close is e-interac payments via email which is still a pain.
Looking at the business charges at Barclay's, the transfer is either 35p ($0.55) or free, depending on the account.
It depends on the bank. Mine gives me 5 free transfers per month and then it's 300￥ per transfer after that.