Amazon offers Prime members Grave of the Fireflies on Blu-ray for $9.99 with free shipping. (Non-members can spend $35 to bag free shipping; otherwise, shipping adds $4.98.) That's tied with our mention from two weeks ago as the lowest total price we've seen. (It's a low now by $6.)
Note that although this item is temporarily out of stock, it can still be ordered for delivery when available.