I think having a moderately active guild accomplishes this just fine. You can see who has what patterns by switching the guild member list to "Professions", tick "Show offline members", and click "View All" on a profession to search through everything in the guild. If a guildy doesn't have it, spam trade or buy in the AH.
I don't see how a for hire board would solve much, unless postings would disappear when the crafter is not online or not in a major city.
You don't factor in what it took the crafter to gain said recipe; it could involve a tortuous rep grind (Firelands/Shattered Sun/etc), a raid, an insane amount of gold to buy, or even a lucky drop after farming 100s of mobs or instance runs. Sorry but if you asked me to use such a recipe without paying the price that I deem to be reasonable, you aren't going to be getting the craft from me. For instance there's no way I'd drop 15k gold on a recipe and then craft that item for some random person for next-to-sod-all.Yes they have the recipe, but in the end I did 99% of the work, collecting mats, and they are simply taking 2 seconds to click a button. I set my own tip. And that's all it is, is a tip. I'm not paying them, I'm thanking them.
There are some items that I simply won't craft for a fee because those items are so rare that I'm the only regular seller on the AH. Then we see how much you want that item. You can either pay the price I dictate on the AH or otherwise choose to grind/raid/buy the recipe (remember you said this is only 1% of the effort) yourself.
Dragonslayer Hoddie - pretending to know what I'm doing!