keep this and you'll be a millionaire by tuesday!
I think there are three issues that make things a bit harder...
;-)
At some point people start seeing real money as opposed to more neutral percentages, as in that amount I'm up or down or whatever right now is worth a good meal, good watch, good holiday, good car, etc, etc, and then they start breaking their rules, holding a losing trade longer than they should, hoping it will turn around, while pocketing a winner too quickly...
then there will always be the odd chop-chop days where you will be giving back to other peoples pockets...
and finally liquidity will start making things harder at some point for the scalper, and actually make continued compounding impossible eventually.
Although to be honest thats at a level that to all intents and purposes can satisfy pretty much every demand under the sun already I'd say.
EG see some of trader dantes
prop trading colleagues who started with zero and now have tens of millions.