sonalee,
I applaud your bravery in asking the question and admire your honest curiosity.
I enjoyed your post asking how to delete the thread as it seemed as if you had innocently stuck you hand unsuspectingly into a nest of hornets. But, no, they are not angry hornets!
They are people who enjoy in different ways (and a lot of the same ways) stamps and the study and collection of them.
The stamps I have now were bought for approximately $3000. I had a lot more years and years ago. (That sounds like a fisherman's tale, the fish was thiiiis big!

) If they were sold, depending on where they were sold, to whom they were sold, when and in what quantity(ies), they would be worth a bit more or a lot less. The old perceived value idea.
Sometimes, if I really wanted a stamp or stamps I would pay a lot more for it. Other times I got a good deal. (I thought so anyway.)
I remember my dad (father) learning a lesson about the perceived value of stamps when I was young. My grandmother had passed away (died) and my father was responsible for taking care of the estate. My grandmother kept every envelope that ever passed through her hands. My dad got a Scott catalog from the library and he and the rest of the family (me too

) spent a week of summer vacation valuing the stamps by the Scott catalog.
Then he loaded up all the stamps (boxes and boxes) on top of the car (in a carrier) and took them downtown to the stamp store. They, of course, only offered 10% - 20% of the Scott value and then only for the ones they really wanted, not all of them. My dad had quite a red face as he loaded all of the boxes back on to the car. He had assumed that he would get the catalog value or a large portion of it.
Some of the value in a catalog is the cost of having a dealer handle it and present it to you. More expensive stamps are valued more by their rarity and their demand (which changes sometimes). Example: the demand for a ship stamp today will be high. Tomorrow, (in the future) maybe Enterprise starship stamps will be of more interest. (?) Animals are always valued but which animals and when? What if their was a Martian animal and there were stamps made of it. Would you want one? I would! (If it was cute and cuddly and didn't eat me).
I am not an expert in any sense of the word. I just enjoy the study of stamps and history. I do, of course, have the collecting bug and tend to accumulate (my perceived value of 'If I enjoy one stamp then if I have 10,000 it will be heaven.') (Well, not always, but sometimes . . .)

.
I myself gave up on the whole idea of investing a while ago. (That is not to say it is a bad idea!) I still like to get a deal and if I can sell it for more then that's a bonus. But it is more the stamp itself, its' history and meaning to me, that intrigues me and makes it of value to me.
So, the $3000 of stamps I paid for are worth to me, oh, maybe $10,000. To you they might be worth $200 only. If you enjoy stamps as a study of interest then the value is more. If you don't really care then it is the value that someone else perceives them as having.
Thank you for asking you question!