Shneibel has a very good point, say for example to further stress test the idea:

Me and a buddy have the materials to make a high end piece of gear. But we are fairly certain while we can craft the item that there is a very high chance it will break. So to completely eliminate that problem he puts the materials up for an Adventuring Leve, I accept the Leve and craft the item...it fails...I attempt again...fails....attempt again....success! Rinse and repeat and not only can you have 100% success on any synthesis but you can effectively inflate the markets with a mass production of high end gear. (yes, I know it would lower the prices but like a real economy you need to have a healthy "supply and demand" or the economy will crash and burn; See: Earth circa 2000 [lol])