I would argue that the exchange of goods that takes place in a potlatch is so different, socially and economically, that it should not be considered trade at all. The Potlatch ceremony is a highly ritualized display of affluence that is primarily exercised by conspicuous gifting and destruction of property. It is a status maintenance vehicle where the host gains considerable admiration and acclaim for his wealth and generosity. While it is understood that gifts given in a potlatch will be reciprocated, in time, by gifts from the receivers, it is not really functioning the same way as what we would generally term trade. Jay Miller provides a brief but informative description of the potlatch here.

Trade is an ancient practice in the Northwest, dating back 6-8 thousand years ago judging from Olivella shell beads found in the Northern Great Basin and the Plateau. Trade was incredibly important important in getting desirable materials to people who needed/wanted them, but I can find no evidence that it was in any way ritualized or functioned in some way to maintain social hierarchy, fidelity or affiliations like potlatches did. It was primarily the simple exchange of goods for other goods of agreed-upon value.

I discuss trade items and routes, goods and other stuff at length in this post. There are some good references there as well.