This is fair, but as a milestone in long-term self-sufficiency, creating a $500/mo app is significant achievement.

Saving $150,000 is, too.

Which is more likely to lead to true self-sufficiency? Barring other possibilities, the savings. But given human response to positive feedback loops, a successful dev often becomes a more successful dev overtime. Hence, I favor the "first app I wrote that made $500/mo" is more significant.