As a dealer/collector I can offer several pieces of advice that will keep the prices you pay for chips as low as possible:

1) Buy from a dealer that will let you return the chip you purchased for a reasonable period of time (30 Days) and even longer if the information said dealer offered about the chip was false. Make sure and establish these guidelines prior to money changing hands.
Within the last few years I've had very good luck with my fellow dealers when I've made sure I can return a chip or chips if a quanity hits the market.

2) Do not go out of your comfort zone when purchasing chips.

3) If the sales pitch is strong, beware!