They were loot during the Halloween event. There are so MANY of them, we asked the devs to please spay and neuter them!
But seriously, people were and are still throwing them away. I do sell them on Napa for about 1000gp - but only after I color them (with natural dyes). I have dyed a few black, and they sell for much more. I also did one in white and auctioned that one - got 300k. Plain, well, not really worth selling/buying as many people have (literally) hundreds.
If you don't already have one, then keep it. They are kinda cute and when you turn them on they do meow.