I was just digging for a filler item for my Etrian Odyssey III order, and I noticed Amazon seems to be having some Blu-ray sale going on. I haven't been paying a lot of attention, but the cheapest I've spotted Advent Children for before was $30. The MSRP on the Blu-ray was obscene considering anybody that wanted it already picked up the DVD, but $15 seems ok for an upgrade.
http://www.amazon.ca/gp/product/B001WG750E/ref=ord_cart_shr?ie=UTF8&m=A3DWYIK6Y9EEQB
http://www.amazon.ca/gp/product/B001WG750E/ref=ord_cart_shr?ie=UTF8&m=A3DWYIK6Y9EEQB