Many/most strategies become less profitable percentage-wise as you scale up the trading volumes. You end up pushing the market around and affecting the pattern

Many/most strategies become less profitable percentage-wise as you scale up the trading volumes. You end up pushing the market around and affecting the patterns upon which you rely. If they've found some pattern that very reliably makes 40k to 50k a year on a 300k investment, with downside semivariance similar to the S&P 500, they're beating the market, but maybe the pattern will never make more than 80k a year, even with infinite bankroll.