I wouldn't say that economic motivation is a determined factor for Flarum devs. Time is the main issue. As the core team have expressed before, they have their real life going on, studying and working, and so on. It's true that development has been slow recently, but IMO this is because Flarum is already an stable version, without any major bugs that require a new commit to solve it.
As far as I have read, most of the things remaining to reach an 'Official stable version' is on internal discussions between the core team.
Let's also not forget this project started as a hobby for them and even though it was considered as such, Toby dropped college for a year to fully focus on Flarum.
Finally, Flarum is a project that started really recently. It's been like almost 3 years since it's beginning, and comparing it with other big forum softwares, like SMF (which is supposedly developing a new release since 5 years ago), phpBB which took more than 7-10 years to release a full version, core devs are getting there in half of that time ?
