i have a formula ive been using since i started in the trade.
i make a deal at minimum 15% off or/and no tax...
our sales tax is 12%, so usually i just offer to pay the list price all in, or something just below it.
usually it works like this:
'how much are those?'
'195'
'ill pay you 190 all in'
or if im buying something big ill request another tool like a plier/driver for free.
and he never says no.
if all else fails i make up the price i WANT to pay, and tell him MAC is selling theirs for that price.
i know hes got kids to feed, but so do i. and its a business, i just barter til we find a spot that works for both of us.
buying in bulk helps. i get my biggest saving by spending more in big chunks, you have more leverage than buying one thing a week.
most ebay stuff is automotive, the tools i require are generally not available, more 1/2 and 3/4 stuff.
although i did buy my KRL on ebay for 50% off in as new condition