Digging into the consignment code, I can see that there are four weights added to the sale probability - Skill, Value, Frequency and Age (0.1, 0.2, 0.2 and 0.3 respectively). I'm not 100% sure on the last two - frequency of attempting to sell it? Age of the item? Thought this might be some useful information. There's also stuff about probability X vs probability Y, but all the Maths that's going through my head right now is basic trigonometry.