After 40 years of buying, selling and trading banknotes and coins, I would have to say that "reference guides" are just that ...... GUIDES.
Reference guides may help to place a particular coin or banknote in a ball-park price range, but that is the extent of their usefulness.
Reference guides will give an indication of which coins or banknotes that are worth more or less than others.
However, these are only "guides". It really depends on supply and demand.
It really depends on how badly the buyer, who sees your coin or banknote, wants it for himself.
It also depends on the seller's circumstances and how badly he needs the coin or banknote sold.
