You are underestimating how low cost this is compared to anywhere else. The issue with most low cost commision schedules is that they tie you to some other requirement, either account minimums, volume requirements, monthly platform fees, IRA vs Standard brokerage, etc
They have none of those...just a low flat transparent rate, that's it. How is 5 bucks expensive for the small trader? That's essentially $2.50 per trade. Anywhere lower and you gotta meet requirements and jump through the kind of hoops I mentioned above, and the small trader can't meet those. For options esentially $.50 per contract, no ticket fees, no volume requirments, no minimum charges, etc.. nothing.
The most mind blowing rates are the futures and futures options rates. That's effectively $2.50 plus clearing roundtrip, REGARDLESS of product. That is yuuuge!! No one else can match that!
These are industry disrupting rates, especially for entry level trading...