The obscure financiers who launched the shell company that is taking former President Donald Trump's social-media venture public are poised for a big payday if the deal gets completed.

The total windfall would stand at about $400m at the stock's current price, after shares skyrocketed sixfold following the deal's announcement. The pay framework isn't Trump-specific — it comes from the distinctive structure of special-purpose acquisition companies, or Spacs, such as Digital World Acquisition Corp.