Joke or not, it really doesn't matter so much that I'm upset about.
I'm just saying, if it's a joke, it's a poor one, and in the end calling it a joke is just attempting to thinly veil the obvious implications of the message which are "buy my EP or else I'll quit." Adding a "JK" to the end of the statement doesn't really clear away the threat.
Now, I completely agree with Chris, that bands like Punchline, although I do not listen to them in particular, DESERVE and SHOULD BE in the top ten on Itunes more than LMFAO etc.
That being said, this is not the way to do it. Joke or not, threatening to quit making music cause you're not number 1 in sales on Itunes is childish.