[mrreality68]

I agree with the above mostly if you have it graded by PSA, SGC etc the grade would go down to the condition ( in part the mail and handling) and the writing etc.
The value also depends on the subject matter or the postcard and potentially even the date and context of the postcard writing. For example I saw a postcard that was about a historical game( sadly I do not recall the postcard) and it was dated and mailed on that game.

But in general I think post cards are still under appreciated and under valued. Although they are in recent years starting to escalate in price spending on the player or team etc on it

I was not into post cards but made the leap about 2 years ago