"Free-to-play is a Scam"

Notch (of Minecraft fame) talking about its next game Ox10c:

@KiiLLBOT f2p is a scam.

— Markus Persson (@notch) April 3, 2012

I don't understand the economics behind Free-to-play. I don't want to play games that cost even more through in-app purchases or which display ads.

I have not warmed up to Minecraft but I am looking forward to this game. Hard science fiction and duct tape: what's not to love!