I've knocked together a quick web script to bring together buyers and sellers. It allows you to post the items (materials, gear, recipes) you're looking to buy or sell (including UVs!) and the price you're looking for. The transaction still must take place in-game. The database is searchable, and at the very least will give you some idea of the prices of things. Right now the site looks homely, but it's functional.
Here: http://clockworkmarket.com/
Enter your in-game-name and post your WTBs and WTSs. All postings for materials will time out after three days. All other postings will time out after five days. If you find a posting you like, it's up to you to contact that person in-game and complete the transaction. This site does no actual buying or selling, but it gets you most of the way there. If you click "done" on a posting, it considers your transaction completed at the price you stated. If you click "cancel" it just removes it.
There is, of course, no guarantee, no warranty, and no affiliation or connection of any kind between me and the people who run this game.
I'm happy to hear any comments or suggestions.
Thanks for using the site.
Looks interesting, i would suggest adding an extra bar for number of stacks for sellers. for example selling 10 stacks of 5 shards for ### price, that way its not TOO tedious for the seller to sell many, and its not something where the buyer has to buy a bulk