He also sells:
Brightly Pulsating Crystallized Cosgrove - 1200
Pulsating Crystallized Cosgrove Shard - 900
Dimly Pulsating Crystallized Cosgrove shard - 600
Faintly Pulsating Crystallized Cosgrove shard - 300
All prices in Brellium Tokens.
Incidentally he will also buy back unwanted purity augs for half the value he sells them. Though going by what the other posters here have said, he'll only buy back stuff that you have unlocked based on your faction/progression.
[Fri Oct 29 16:18:41 2010] Dermott Saltagger tells you, 'I'll give you 150 Brellium Tokens for the Faintly Pulsating Crystallized Cosgrove Shard.'
[Fri Oct 29 16:18:42 2010] You receive 150 Brellium Tokens from Dermott Saltagger for the Faintly Pulsating Crystallized Cosgrove Shard.