I remember reading, probably 25 - 30 years ago, that the profits from licensing the toys and merchandise paid the producers more than the show itself. Surprising, for something that was such a part of the pop culture of the time, that it only lasted the three years. Especially, when some of the biggest stars of the day were vying to get a guest star spot on the show.
Given how limited the choices (with only 3 networks) were at the time, in reality their ratings were probably better than most shows in the air today, dwarfing them in the total viewers category by comparison.