the whole point of the "priceless" meme is that the priceless thing is supposed to be something negative
Um...not where I come from!
In the USA, the word 'priceless' would (in this particular context and joke framework) be interpreted to mean a combination of "delightfully amusing" and "having a value beyond any price" (see definition 1a & 3 below). Neither interpretation suggests negativity.
'Priceless' is also frequently (and incorrectly IMHO) used as a synonym for the word 'perfect' where I live.
from Webster's Dictionary
1 (a) having a value beyond any price : invaluable (b) costly because of rarity or quality : precious
2: having worth in terms of other than market value
3: delightfully amusing, odd, or absurd
I do think, however, that the last two sentences don't really work. It would have read better if the author left them out.