[(E)]

Cost plus 50% extra for each set of hands is passes through is a simple rule I have used before.
Say pepper is produced at a cost of $100 a pound and passes through 11 sets of hands to get to your corner of the world. Farmer, broker, spice merchant, shipping 1, shipping 2, spice merchant 2, shipping 3, shipping 4, spice merchant 3, shipping 5, spice trader. The end result is pepper is worth something like $8650 a pound after traveling down the silk road. (Which might be a bit cheap historically).