From Goto 10: Retro Computing & Gaming:

The slogan was on the back page of Compute!, a magazine I often bought from the video game store of the strip mall where my parents operated a gift shop. The advert displayed a trio of competing personal computers on the top half of the page, the Apple IIe, the Tandy TRS-80 III, and the IBM PC, the cost of each machine near a thousand dollars or well above it. The bottom half starred a family of three staring at a computer monitor showing the planet Saturn: mother on the left, father on the right, and the son in the middle with his fingers over the brownie-brown keyboard. “The Commodore 64. Under $600,” the final lines of the ad read. “You can’t buy a better computer at twice the price.”