Not necessarily. Many stamps are valued for their cancellations and sometimes the envelopes they are "tied" to.
A stamp is worth more unused
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.
I called a collector and they said it will not be worth anything except 1 cent.
Not sure what you define as an original stamp. A US 3 cent unused stamp is worth 3 cents toward postage. It may have more value as a collectible, but you would have to consult a stamp catalog to fully identify it and get an estimated value. You might try the online version at Mystic Stamps as a starting point.
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.
If you mean the US stamp, it was issued 1990 and about mint .65c used .20c
A 28 cent stamp that is unused can always be used as 28 cents worth of postage. If it is used, it probably has a minimal purchase price of fifteen cents from a dealer.
It depends on the stamp which you have. Although, to be honest, most stamps issued this recently aren't worth very much. Generally, since there were so many printed, it is used as postage on mail!
There is no 1881 Roosevelt stamp. The earliest stamp issued with a Roosevelt, Teddy, was in 1922. Scott number 557 is worth 45 cents catalog used and about $30 in mint condition.
In most cases, mint stamps, those that have not been used, are worth more. In a few cases, used stamps are more valuable. Modern used stamps are typically worth very little, but there are exceptions and the most valuable stamps in the world are used.
The 1940 10-cent stamp is worth $5.00 in mint condition and $1.65 used. (as of Jan. 2011)
A 28 cent stamp that is unused can always be used as 28 cents worth of postage. If it is used, it probably has a minimal purchase price of fifteen cents from a dealer.