Hello inyoni, welcome to Stamp Community!

Every stamp is worth a million dollars!

You own them, and your family, if you so desire of course, and some are priced in the catalogue or catalogued at higher prices that others.
BUT, it all depends on demand and supply also. You might say that the 2c bluish Washington is worth more than any of the others because it is older but the nicked corner devalues it to other collectors who can afford a nicer copy.
When you cannot afford a nicer copy then you can sell it for a good price perhaps.
Years ago in the 70's and 80's when I started up again, slowly and surely, stamps were worth what the catalogue said they were. At least when I bought them from the stamp store on the main street they were. Not when I tried to sell them though.
Each stamp has a story. Where did you get it? Where did it come from? Who had it before you? What did he or she do? Money means something but also caring and love and what the holding of it does for you means something also.
Some of your stamps look in better shape or condition than others, so would be more worth something than another similar one in worse shape. It's hard to tell when starting out, even again.
I could want those and pay catalogue price for them because they were there, available for me to buy. I didn't pay shipping or postage to get them perhaps, or I didn't have to go to a lot of trouble to get them.
But then, when you do pay or go to a trouble, sometimes that makes the stamps seem to be worth more also.
The love of history helps collectors or accumulators or even sorters like I was. I just wanted to sort out stamps, cheap or expensive. But then, over a time, I started to appreciate what a stamp could be worth, Details, details, details are what makes one stamp worth more over another stamp.
Examples:
- Words upside down on a pre-cancelled stamp or off centered or rare cities or rare typefaces or fonts.
- Slightly different colours for the same stamps.
-Different small details of one stamp over another same stamp.
-A beautiful cancel or postmarks or rare postal marking over a stamp with just an ordinary wavey cancel. (I'm a cancel collector too!

)
-Seeming same stamps with a different perforation (wiggly edges) measured in how many every 2cm.
-Different centerings of the design on the paper.
-Different papers themselves.
-Higher denomination values in a set, or a complete set of stamps.
Etcetera, etc. Different topics are collected, different countries, the same country in depth, cats on stamps (a favorite kind of), personal stamps now-a-days, cinderella or poster stamps, mint fresh stamps over used cancelled stamps.
After a while you find out more and more, and there is always something to learn, always something to appreciate. The more you know, the more you realize how much there is to know.