This is not quite right. For trading stocks, you need to factor in the SEC fee above what you pay for commissions. It is a percentage of the total dollar transaction regardless of number of shares. These days the SEC fee is so high that you really can't make money scalping for a 1 cent in/out.
Can be expensive if you trade high priced stocks like AAPl and GOOG. Sec Section 31 transaction fee rate is $22.40 per million dollars sold. so, 100 AAPL at 580= $58,000. 58000 *.0000224= $1.2992 for 100 shares of AAPL.
There is a way to bypass the $1 minimum in IB for trading 100 shares and just pay 0.5. I am not going to tell you how but if you have used IB a lot, you will find it out. A hint: Putting order will not be that straight forward. You have to use one of the trading features that IB offers.