I'll presume what you really mean to ask is "how much do startups typically raise when they go through the 500 accelerator program?" altho some of the raise happens both before & after demo day.
we haven't included the recent batch yet, but the historical answer has been: ~50% raise >$500K ~25% raise >$1M
also, ~1 yr later we estimate ~20% shut down / run out of money, and ~10% raise a Series A of size $3M or more. (that said, looks like these #s continue to improve in our most recent batch #6)
You're mistaken if you think you'll actually raise money AT Demo Day. Sure, there are times when someone may commit on the spot, but that's rare. The point of Demo Day is to meet investors and get their contact info, get that first meeting.
At DD, the entire team should be working the room and networking w/ the attendees. 500's Demo Days include investors (VCs, angels, seed funds, etc), press, platform companies, M&A ppl, potential partners, potential customers, etc.