Fine art

There are at least three ways something can become valuable over time.

1) Desirable and plentiful in it's day, scarce today.
2) Misunderstood (or undesirable) in it's day, therefore scarce, and desirable today.
3) Desirable, but scarce, then and now.

Which is this? I don't know, but good black velvet paintings by popular artists are now bringing close to five figures in the "art" market. This one by noted painter Tang Lao, dated '69, is probably not in that category, but well worth the $20 I spent for it.