Even for things like T-Shits scrapping groups was insane money... I remember I use to go to like a "fishing group" then extract all the users. I would then remove everyone except woman, and market a shirt that said "I'm a Woman Who loves Fishing" ... the other thing was I'd take MULTIPLE huge "Fishing Groups" cross reference users who belong to them all and do similar. Dialing in your advertising.
I used this method to bring in over 250k in a single year.
Selling Shirts to
Specialty car groups, Mustang / Corvette / M3
Dog lovers, by breed.
Sports teams
I was also selling "survival gear" essentially using the same method. I still extract group e-mails, but response is probably 2% of what targeted ads were doing.