invaluable » unvaluable
Spotted in the wild:
- “Unvaluable heritage (or) Corals” (A tourist info page that's genuinely praising coral reefs)
- “Amazing! An unbelievable and unvaluable sorce of info and links. Great Job!” (link)
While some of the occurences are conscious plays on ‘invaluable’ for a sarcastic note, a lot are genuine. I suppose that once people have absorbed the counterintuitive use of ‘in-’ in the word, they start equating any negation of ‘valuable’ with it.
[Or so I thought… but ‘disvaluable’ in that sense is pretty much non-existent. I guess the phonetic closeness has a part to play too.]