Borrow against your Bitcoin thought experiment

You might have heard Michael Saylor said that: Never sell your Bitcoin, only borrow against it. Rich people never sell their apex property.

When I first heard that I thought to myself: How is this even possible, where do you get the money to pay for the loan? So I run a thought experiment:

Assumptions: BTC price is 60k, can borrow at 1:3x collateral for an interest rate of 5% a year

Situation: need 15k for university for a child

Action: Borrow 20k using 1 BTC as collateral (60k) - Pay 1k interest a year, use 15k for university fee, 4k left to pay interest for the next 4 years

Assumption: 4 years later BTC goes up 50% or about 12% growth a year (90k/BTC after 4 years). Since you can borrow maximum a third of your collateral, the maximum amount to borrow now is 30k. You borrow another 5k out to pay interest in the next 4 years.

Rinse and repeat, as long as Bitcoin grows faster than the interest rate of 5% a year, you win from borrowing vs selling bitcoin, also not generating a sale tax from selling bitcoin.

If the assumption keep being true: say Bitcoin keep growing at 12% a year, interest rate is constant at 5% a year. If you decide to sell some bitcoin to pay back all your debt after 20 years, you only need to sell 0.11 bitcoin to pay all debts and interest versus selling 0.25 bitcoin today to pay for said child’s university (Capital gain tax not included in this calculation)

Assuming 17.64% Tax, the decision to sell BTC today instead of in 20 years make you $82,167 worse off, even after paying all interest and pay back completely your debt.

Mind blown ???? Now I understand why people like Saylor are richer than me ????