I feel you, and that's a problem because if you want to tax a billionaires "unrealized" profits, you probably also have to tax some poor shmuck's unrealized 401k profits when they have like 100k stashed away. I'd be cool with higher consumption/sales taxes for ultra rich person items: third or fourth homes, property in the "x" percentile of value above the average, luxury items like yachts or Ferraris. Theres a whole world of solutions, if only we could get the the politicians to enact them.

Or hell, just make them sell their stocks and pay tax on unrealized profits for anyone above like "x" millions. They'll be fine at the end of the day, and it'll dilute their corporate ownership once the company gets too big anyways.