That seems like it's mostly caused by QE policies/zero interest loans (which is already just giving money to rich people). No one's going to take out a loan at

That seems like it's mostly caused by QE policies/zero interest loans (which is already just giving money to rich people). No one's going to take out a loan at 5% interest to avoid 20% capital gains on 10% growth (i.e. a 2% tax). For your unicorn growth billionaire, like someone else suggested, you could require realization at the time you value the asset to put it up for collateral.