Yes, is does. We calculate slippage as the percentage of the quoted price. The value you set will depend on the strategy you are running. Our default slippage cost is set to 0.5%. We’ve based this amount on this work here which is a long-term study of frictional investing costs (Jones, May 2002). If you are looking at running a small-cap strategy your strategy should assume a higher slippage value of up to 2%.
There’s a large difference between what professionals and retail investors pay in brokerage. The default brokerage fee is set on the conservative side for retail investors at $10 per trade.