The demand icon next to items the Market Board doesn't actually correspond to the actual demand in the item. (Heart shaped + number).
That number only tells you how many people put that item in their wishlist, but not the number sold/time.
I put things on my wishlist just to check on their prices all the time, but I don't actually buy the items. So already I am adding inaccuracy to demand.
I wish they changed their demand to actual demand rather than people adding to their wishlist.