Fellblade should be in your list of "expensive" skins....a GOOD fellblade (Especially a good TYRIAN fellblade) is going to fetch a price WAY higher than an FDS/IDS ever will.
Also, just FYI for the TC.....20/20 Sundering and +30 hp Fortitude are the most EXPENSIVE mods, but they are not by any means the best mods for actual gameplay.
I'm not going to go over the math again here, but +5 AL > +30 hp in the vast majority of situations and Vampiric/Furious are typically better than Sundering (Vampiric = > DPS as long as you can manage the degen with a non-vamp weapon in-between battles....Furious = enhanced skill spamming ability which leads to more good things, be it DPS or tanking).
As folks have said, after you deal with max damage, mods, requirement, etc., "best" is just in the eye of the beholder....
Best of luck! --- XBL GT: Loki ISP....GW IGN: Nentslye Woodmaster, Pope Woodmaster I, Silussa Mindraper Clan Leader, XBL Clan Wolfpacklan...www.wolfpacklan.org