just the fact that the original poster is asking this question, will make you say HUH? 100,000 a day, 500,000 a week, sure no problem. Just dumb....
100k per day? Supposing they make an average of 1% per day (the 100k), by the way a very incredible feat; they'll need 10 millions of capital, to make $36.5 millions per year, without compunding profits. Only losers state daily, weekly or monthly performance, as figures may vary greatly over time. REAL Pros only state yearly performance. At most quarterly performance.
Ask him how who enters the trades. To DAYTRADE to make 100k, he will need to hire people to enter trades for him.
Why do you think so ? Maybe he pulls in 3-4 ticks daily in the ZB with 1k cars, or trades forex. All a matter of account size.