If they weren't mostly lost they couldn't be valued antiques in the first place as they would still be common. Of course scarcity does not guarantee value either. The rare also needs to be valued by a current generation essentially. Old and rare computers or tools may be more valued now by nerds than good China that nobody actually uses from the connection to history and the rise but give it a few generations and they may wonder why they paid so much for that old obsolete back then piece of junk.

Heirlooms are more about personal sentimental value than anything mass market. Nana's old worn out chair could be contended for in inheritance even though you would have to pay to get rid of it instead of selling it.