Yes, I agree, there are "Buck Rogers in the 25th Century" fans who don't even collect toys or Megos who want them. Having the Mego Starfighter back in the day, and collecting on Buck Rogers original costumes and props now days I have been watching them for years and they just don't seem to show up much. I would definatly consider them rare. Plus they break easily, when compared to Kenner Star Wars toys the plastic seemed very fragile, which may add to their scarcity.
It seems that you see the Draconian ship more often, maybe less desirable as the Starfighter has such as classic look. The gray plastic fronts and engines should be a Dr. Mego replacement part.
"Your future is what you make of it, so make it a good one" (Doc. B BTTF pt. III)