To have a band that rocks without any bull-crap on the side. No airplanes, hotel rooms, fancy tour buses or light shows. Simple tour van that barely fits all the equipment and the few musicians - show up to a gig, play and move on, sleeping in the van or borrowing a couch for the night. Also requires that the band can actually fulfill the 'jam' part - you have to be able to rock once onstage.
note: this does NOT mean you have to have cheap equipment, only that your actual musical life is lived at a minimum.
The Minutemen's do-it-yourself attitude made them experts of jam econo.