Quote:
is there a non costly way to get the scotch tape off without destroying the stamps?
None worth the effort especially considering used modern stamps have little value in the best of circumstances. And the real frustration is the glue will discolor the stamps in time anyway as it is never fully removed.
Be happy you were not assessed postage due. In the USA covered stamps are invalid for postage.
Edited to add three rules to help preserve your stamps:
No tape.
No rubber bands.
No Crystal Mounts.
They are death for stamps and postal history.