Trophies are bought by the NPC market and never get bought by another player (unless they're sold as a result of the Death system that auto-lists possessions).
They would sell at [1 - ( .02 + (.2 - .04*Tradeskill) ) ] * 2 *(RMP/Batch)
Lemme just check a recent sale and see if I have it right:
You have received 1,404,000 credits from the Market with the following message:
Sale of the following assets: Thranta Tail Thranta Tail, Falumpaset Fetlock Falumpaset Fetlock, Duracrete Skin Duracrete Skin, Hawkbat Beak Hawkbat Beak, Granite Slug Eye Stalk Granite Slug Eye Stalk, Boma Tusk Boma Tusk, Varactyl Plume Varactyl Plume, Varactyl Plume Varactyl Plume.
Thranta Tail x 1 (75k)
Fetlock x 1 (300k)
Duracrete Skin x 1 (275k)
Hawkbat Beak x 1 (50k)
Gslug Eye stalk x 1 (50k)
Boma Tusk x 1 (50k)
Plume x 2 (500K each)
Batch Quantity for Trophies is 1.
Total RMP = 1,800,000
2* RMP/Batch = 3,600,000
3.6 mil * [1 - ( 0.22 )] = 2,808,000
Okay, so there's an error in the rules. When selling Trophies, you get only RMP/Batch instead of 2*RMP/Batch, but otherwise it checks out.