I think the price discrepancy derives from wildly fluctuating copper prices. When the suppliers buy it at a good price they can sell it at a good price. The higher price comes from the supplier not wanting to buy the wire for you at the current steep price. The other supplier already has the wire from an earlier purchase that was at a lower price. That scenario is a guess. You can ask them where the price comes from, but of course do not shop the numbers out.
The other bummer is the ethics of not cherry-picking the replies to your requests for pricing. You have to already know from prior experience where your best price on commodities like four square boxes comes from and do not add that item to your request for pricing from other suppliers.
Sorry, just read your post and you are buying Aluminum, so my theory doesn't hold much water!
