Depends on how good the rest of the app experience is I suppose. For example, I think people who like SN are the ones least likely to try and optimize their zap earnings (at least, not in a hyper calculated way). And the causality probably runs both ways 

SimpleStacker

Stacker Saloon

saloon

Mhhh, didn't think about that, thanks

But I imagine the UX is terrible, so I might actually prefer watching ads instead, it might have better UX, lol.

Pay-per-message also punishes you if you're the type that sends multiple smaller messages instead of one bigger one. Or you just keep editing old messages if possible, for as long as possible. Or do edits also have a fee?

See? I'm already trying to optimize the fee, instead of having a great experience.

However, I did not try it out, so maybe it doesn't actually work that way.