“共交易3000-5000万股，而利润很是微薄，大约20%”

我的理解加假设：Assume the stocks that you have traded have an average price of $10/sh, then your transaction in dollar amount is $300~500M. Your profit margin is 20%, therefore your profit is　$60~100M.

不对吗？

$10/share 很保守啊。一年　$60~100M　毛利也很牛啊。