Honestly I have no problem with monthly fees for software you use every day, or frequently, for professional use. I'm fine paying monthly for things like Adobe Creative Cloud, Microsoft Office, and 1Password. Those are all desktop apps, albeit with a cloud component that I mostly don't use. I easily get my money back 10x over (likely more) based on the income I generate with the apps.
The pricing here seems targeted at media folks who do e-mail creation for a living. Assuming it works well, it's likely a bargain for them as well. But I have to imagine that market is rather small.