Mana Mushrooms

Plenty of market information here, including pricing and other useful information about sales and advertising on a broad scale, separated by region:
USDA AMS

From the site:
"In 1990, the Mushroom Promotion, Research and Consumer Information Act was passed by Congress to strengthen the mushroom industry’s position in the marketplace, maintain and expand existing markets and uses for mushrooms, and develop new markets and uses for mushrooms. In 1993, the Mushroom Council was established to carry out the direction of this act."
Mushroom Council

One of the best sites to support the industry of mushroom cultivation.

AMI