Many investment executives who back special-purpose acquisition companies are scoring big paydays as more deals get completed. Some of their clients are missing out.

The divergence results from the varying methods Spac creators use to share the lucrative incentives known as the "sponsor promote." It typically consists of deeply discounted shares and other securities executives receive for risking capital to set up the Spac and vet a company to take public. The promote typically allows creators to make tens of millions of dollars on paper on average — sometimes several times their initial investment — even if that company's shares fall.