A pyramid scheme is an investment where investors profit from the recruitment of those below them. Capitalism is the privatisation of the means of production. The two are far more similar than they may seem.
A pyramid scheme exists to benefit the highest-ranking investors. Capitalism exists to benefit those who own the means of production, who are known as the bourgeoisie.
While the situation is obviously unfair to the lowest-ranking investors, they accept their exploitation at hands of the high-rankers by telling themselves that they'll eventually be high-rankers themselves and will get to exploit their own low-rankers. While the situation is obviously unfair to those who must produce via the means of production, known as the proletariat, they accept their exploitation at hands of the bourgeoisie by telling themselves that they'll eventually be bourgeoisie themselves and will get to exploit their own proletariats.
However, the low-rankers' hope is misplaced, and the vast majority of the time, their position changes little as they spend their lives enriching the high-rankers. However, the proletariat's hope is misplaced, and the vast majority of the time, their position changes little as they spend their lives enriching the bourgeoisie.
Capitalism and pyramid schemes are both closely related systems of justified oppression where those being exploited assume that they'll one day get to be the exploiters and therefore choose to uphold the status quo so that they don't undermine their eventual rise. In both cases though, this acceptance of oppression is almost never rewarded, with the only beneficiaries being those same exploiters. The only significant difference between the two is that capitalism relies on the development of a naturally-occuring hierarchy via the market while pyramid schemes actively create and maintain a de jure hierarchy. Since an artificial hierarchy is more effective at upholding the status quo than a natural one, it can be argued that a pyramid scheme is simply capitalism taken to its logical conclusion.