It is worth the cost of the stamp.
how much did a postage stamp cost in 2016
About $2.00
Most stamps will show the value of the stamp somewhere on the design.
a stamp in Montana costs 44cents
Check your stamp at the link below.
I have the stamp in good condition. It was for 15 cents.
44 cents per stamp
In 2017, the cost to mail a standard letter within the United States was 49 cents for a First-Class Mail stamp. This rate applied to letters weighing up to one ounce. Additional ounces would incur extra fees, with the price increasing by 21 cents for each additional ounce.
The E stamp had a picture of Earth on it. The face value of the stamp was 25 cents.
There isn't any stamp that is called a penny purple. You need to describe the stamp - include country and if you can date and what is on the stamp.
Without knowing which stamp, it's pretty much impossible to value.
the postage stamp had cost $00.32 in the year 1993