Infamy from tests of selling of illegal items is MarketSellPrice = S, S+(S*0.Modifiers) = O, O/250 = Infamy, Examples Crystal Meth 1505/250 = 6.02 Infamy Per Sold. Scotch 943/250 = 3.772 Infamy Per Sold. Getting 7% Shakedown (2,000) will get you Scotch 943+(943*0.07) = 1009.01, 1009.01/250 = 4.03604 Infamy Per Sold. Making that a 7% Increase to Infamy gained as well (Cartel take away doesn't seem to effect this). This takes market crash into account tho.
So to maximize infamy gain having anything that increases sell price as well as selling when market isn't crashed will increase your gain. (This is at least for now hopefully this doesn't cause the % gain to get nerfed)