I'm not disagreeing with you. In fact I'm pretty much agreeing -I'm saying 10Kh is necessary but not sufficient.
You are saying:
10Kh of practice + tutoring costs + (implicitly) not having other responsibilities to block the learning either directly via work or whatnot or indirectly via emotional stress.
That 10Kh is in your equation, but isn't the only part of the equation. That is it's necessary but not sufficient.