It took a long time before the PlayStation 3 was profitable.
Obviously, considering Sony's approach to their latest console (cheaper to manufacture, lower retail cost, etc.), they didn't want a repeat of history.
And so far, the strategy is working: Speaking during a business meeting, Sony president Kaz Hirai said the PlayStation 4 is "already contributing a profit on a hardware unit basis." As reported by Japanese source AV Watch (and translated at NeoGAF ), Hirai said this result has formed a "very different business framework from that of previous platform businesses." Basically, this means the PS4 is already profitable; the PS3 and PS2 were sold at a loss for quite some time.
The PS3 especially racked up big losses but that won't happen with the PS4. Hirai also said that over half of PS4 owners had subscribed to PlayStation Plus, which we've heard before and it's hardly surprising, given the necessity of Plus for online play.