This article is from the Macintosh for sale FAQ, by Elliotte Rusty Harold email@example.com with numerous contributions by others.
Nothing is more helpful in convincing salespeople to
lower their prices than a competitor's published ad or written
estimate showing a lower price. This works even if you have no
intention of buying from the competitor in the first place (for
instance because it's a mail order ad and you don't want to buy
through the mail). Except on the cheapest systems you should ask
that the salesperson beat the price by at least $50 and maybe as much
as $300 on high end systems. Justify it on the grounds that you don't
want to have to shuttle back and forth between dealers to keep
getting a $10 drop in price every time.