This article is from the rec.audio.* FAQ, by with numerous contributions by Bob Neidorff others.
Street price represents the price which you would pay if you
went to a store and bought the product. It isn't a sale price
or the published price, just the actual, common selling price.
Some manufacturers tell their dealers to sell right at list
price. Others provide a low enough wholesale price that the
selling price can be significantly below "list price". List
price is generally meaningless, so street price is a more
realistic comparison price.