Hmm... it seems to me that the service is exposed to more risk for higher transaction amounts (say, something is crooked, or just goes wrong and the service win

Hmm... it seems to me that the service is exposed to more risk for higher transaction amounts (say, something is crooked, or just goes wrong and the service winds up holding the bag). That's not to say that the current fees are necessarily fair, but it does make sense to me that larger transaction amounts should be charged more.