It depends on the specific stamp and the type of flaw. A flaw caused by a cracked plate can be important, but may not create a large change in value.
A stamp is worth more unused
A 5-cent 1946 Roosevelt stamp is worth about $1, but it depends on the postmark and the design on the stamp. Some postmarks of this stamp could be worth $11 or more.
The value of a Margaret Mitchell stamp can vary depending on factors such as condition, rarity, and demand. Generally, a single Margaret Mitchell stamp can range in value from a few cents to a few dollars. It is advisable to consult a stamp collector or appraiser for a more accurate assessment of the stamp's worth.
It depends on what the flaw is, post a new question with more information
It is worth the original cost of the stamp.
A used stamp is seldom worth more than a mint stamp. However, that can vary considerably. The stamps of some countries, such as Tonga, are worth more used then mint. And a used stamp on an envelope could be worth a great deal depending on the cancellation and other factors.
Most collectors prefer to have the stamp in its original position, on envelope or document. This shows the usage of the stamp as it was intended and will have more value than the stamp by itself.
It is worth two cents. It might be worth more if someone famous licked it.
Your stamp is not rare and is not worth anything. Most German stamps of this era are worth far more if they are used, and the cancellation will ultimately determine the value.
The Elvis stamp is the best saleing stamp in millions were sold. People purchased them and saved them hoping they would be worth something down the road. But because there were so many sold there is not real value to them . Just there face value of the stamp. First Day Issues are worth more and so would block stamps of the Elvis stamp.
It is worth the cost of the stamp.
Two-dollar bills are generally worth two dollars. Adding a postage stamp to it wouldn't affect the value if the bill. The stamp itself, if rare, might be worth more than two dollars.