I am in the shard selling business so just a quick overview on what you can get for them
Fire: 100 each, maybe 150 in front of BS/armor guild
Ice: 75 maybe, they dont sell that well.
Earth: 150 each across the board
Water: 100 each across the board
Lightning: 150 each across the board
Wind: 150, 300 if in front of Carp Guild
All these prices are what I easily sell them at(except ice, which doesnt move well) and ive sold thousands of each, in the last few days at these prices.
Price of crystals will vary depending on wether people actualy use them or not, but generaly speaking, Fire is the one that sells really well, the others, eh.