nyse is untradeable. The NX system is TOO controlled by the specialist, and he can halt your so called electronic order if he wants to.
How can someone scalp when he needs to wait a literally UNKNOWN amount of time for execution?
Actually their execution sucks so bad that almost every week there is more and more talk and suggestions to make the nyse fully electronic or to at least add liquidity in its issues in other electronic markets.
You can take swings trades in the nyse but forget scalping.
And as to the question why do props work only with nyse, well there is a very good answer to that.
The usual prop strategy is "buy 10,000 stocks on the open, weed out the losers, maybe you'll make money and maybe you won't buy we'll make a hell lot of commissions".
That means they provide quite a lot of liquidity to the nyse, which in turn almost certainly pays them some sort of rebate.
Cheers
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