The OP was asking for an idiom which
describes the current state of the sunglasses (from the example), not one that describes the initial purchase.
So it's not so much that it was cheap to purchase, but that it would be relatively expensive to replace.
To me, that speaks of an item which was once cheap and ubiquitous, but is now rare and hard to find, commanding a premium due to scarcity. A few examples:
- A popular soda brand alters its flavor; disappointed consumers pay a premium for the remaining stock of the old formula
- A legal product becomes illegal, for example a slightly-too-dangerous toy
- The newer versions of a product are cheaper and flimsier than the old ones
In such a case I might say
A decorative object or toy which was produced for a limited time may become a
collector's item, in some cases prized more for its rarity than its intrinsic worth.
Further from the example of the sunglasses, media, such as music, books, and especially movies which were unappreciated at the time of release may become a cult classic