I have a friend who's a professional flea marketeer, he told me that
for an 8 AM opening time, he's already walking around at 6:30 AM buying
stuff- and by the time the public gets there, the stuff that's worth
$200, that was selling for $25-50, is gone- other marketeers already
bought it

then, they put it on ebay when they get home

what doesn't sell, goes back to the market 2 weeks later

constant cycle

the average joe can get lucky here and there, and find some stuff under
bushels, etc., or from someone that set up late, or someone that
finally moved off a high price

but for the most part, the VERY early bird, gets the worm