Just looked up local prices:
Group 24 (70-85Ah) = $100
Group 27 (85-105Ah) = $105
Group 31 (95-125Ah) = $125
So, as usual costs go up!
Still no need to spend $250 on a battery.
In any case, you don't need a big battery if you're not going alternatorless. Just remember to top off once in a while.