The worth of a stamp is determined by some aspects including:
The number is available on the stamp collection market.
Request from stamp collectors inside and outside the country of source,
The condition of the stamp, a damaged stamp is cost only a division of one in fine condition.
Opinions as to present or future worth,
The current event may momentarily raise prices.
The place of buying or sale. Costs vary according to where the deal takes place. Values differ from country to country for the same stamp and values realized at a stamp collections auction may be different from those claimed by a dealer or in a private sale among collectors.