Fees such as trading costs are a percentage of trading volume.
Therefore, the more money you are managing, the higher your trading costs. (i.e those costs are "fixed" but its a "fixed percentage" rather than a static number.)
In that case, how can the rate be fixed or does that mean that the hedge fund limits its trade turn-over. In other words, if your trading fees are 0.2% and your trading volume is 10 times the capital raised, you already burned through your management fee.
Therefore, the more money you are managing, the higher your trading costs. (i.e those costs are "fixed" but its a "fixed percentage" rather than a static number.)