Founder of a solo dev $500k/year agency here.
10000%.
I topped out around $500k/year. Just naturally settled there after aggressively optimizing my process.
This is with 1 dedicated sales person who's entire job is to minimize and replace churn.
Good to see there is a mathematical proof haha.
I've been exploring productization and have made it a goal for 2024, to possibly breaking this ceiling without hiring any one else.