Low fabrication makes you lose 1 component - starts at 100% chance, then lowers 10% per point and caps at 50%.
Low dexterity makes you lose from 0 to 2 components - a roll of 3d4 is made against your dexterity. If your dexterity is lower, you lose 1d3-1 components.
Item damage affects salvage the most: for every single material not lost yet, there’s a 0.8^damage chance for it to survive. For damage in [0-4] range, that’s 100%, 80%, 64%, 51%, 41%. So if your item is tattered, expect to get less than half of the material back.