Best deal on Killzone PS4?

Just wondering currently the best place to purchase Killzone on PS4? I'm looking for below $20 if possible.

That seems about the best deal. If you have GCU from Best Buy that would basically take away the tax.

It seems like I've seen that game used during a GameFly flash sale for around the 15 dollar mark the last couple months if I recall correctly.

Thanks. I guess I'll just wait n see as I'm not in a rush to play it.