JOE PYE WEED Eupatorium purpureum

Habitat: Joe Pye Weed is a North American native perennial herb found in moist woods and meadows from southern Canada to Florida and west to Texas. Cultivate from seed or root separation, with partial shade to full sun in rich alkaline soil. Growing to a height of about 12 ft. it makes a handsome addition to any garden or as a privacy border.

I have a yard full of Joe Pye Weed. Judy says the seed sells for $36/oz. I'm wondering how much it takes to make an ounce?