[Bitcoin-development] Cost savings by using replace-by-fee, 30-90%

[Matt Whitlock]

On Tuesday, 26 May 2015, at 11:22 am, Danny Thorpe wrote:
> What prevents RBF from being used for fraudulent payment reversals?
> 
> Pay 1BTC to Alice for hard goods, then after you receive the goods
> broadcast a double spend of that transaction to pay Alice nothing? Your
> only cost is the higher network fee of the 2nd tx.

The "First-Seen-Safe" replace-by-fee presently being discussed on this list disallows fraudulent payment reversals, as it disallows a replacing transaction that pays less to any output script than the replaced transaction paid.