30 usd for special back cover enabling larger battery would be ok with me.
My DX90 now has close to 150 hours on it and I've had my first "proper" session with it - 6 hours straight. I'm still very, very impressed by the DX90. The one word that really stands out for me is "clarity".
The DX50 is great for the money, but the DX90 is just great, period. My DX50 will be up for sale soon...
There also this battery
very expensive 90$ but 2 times stronger than the origianl of galaxy 3 the only problem she is wide and will not fit to back door of dx90