Which real world do you live in? Real businesses spend a good percentage of their efforts in cutting costs. And if they have a large consumer base they push newsletters too, then yes, as an agency, I can tell you that a lot of clients will make the switch.

There a bunch of open source self-hosted newsletter systems doing well (oh, and they're mostly subpar). I like the direction in which sendy is heading and with the amazon ses edge to it, its a great great idea. If sendy would throw in a few more features like multi-user login and access control, I'll make the switch and will convince a few of my clients too.