Check out Churnham and Burnham Securities in downtown Manhattan. They charge 5% to buy and 5% to sell. Very reasonable in my opinion.
It sounds like they want to deter clients that don't do volume. That's why there are more than 1 prop firms out there, depending on what your needs are, I'm sure you can find something more suitable for your style of trading....
5% would be based on the dollar amount of the trade, so a $50,000 trade would cost $2,500 in commission each way. By the way, I was only joking; no such firm exists.
No but I've heard it exists, what's bad about these platforms is that they're not available during off trading hours so you have limited time to go through them