Things that sell well are Mega Rich + Planets (Artifact will sell for the most) and Colossal + Mega Colossal planets or planets which can become such. For example, a Very Massive Icy with good stats will sell well because someone could turn that into a 17x, 22x 17x (Mining, Artifact, Research) Mega Colossal Planet which would be very nice to own indeed. Don't waste you Mass-Surface Melters (and other artifacts in this mission chain) on planets you think are good; they're probably not that good. Save them until you're Taltherian. If you don't know what Taltherian is, then don't fret. You'll lean in time what each thing is.
