The odyssey is $250. The Diehard Platinum is $220. The Odyssey has 880 cca, Diehard 850. Odyssey makes a group 25, diehard does not, I'd have to use a spacer to fit a 34. The group 25 weighs less too.
Also, I think $250 is fair for the performance I expect. The Optimas were supreme 12 years ago. They still cost the same as 12 years ago however. One way to hide inflation is to decrease quality. If their quality were the same as when they came out, I would expect them to be about $250 now too.