Twitter has 5,200,000,000 shares of capital stock, sold at $53.26 per share — and this can change quickly.

In order to buy more than half (2,600,000,001) shares: you would need $138.48B. For scale: this is approximately fifty-six Donald Trumps, or five percent of the federal deficit for 2020 (rounding up). Keep in mind: Twitter doesn't pay dividends, so you wouldn't be making any of this money back.

This is assuming investors are actually willing to sell — and they probably won't be if you only pay market price. Ideologues like Jack Dorsey will probably never sell, preferring to grip onto power like a Middle Eastern dictator.