Well, where I buy my hay, I only buy a mini bale because, my bunnies don't eat alot of hay. The mainly eat fruits and veggies and feed of course. But the size of the mini bales I buy are about the size of a key-board... I hope that helps.
I can't get different size bales here- I buy 100 pound bales at my normal feed store. When they are out the bales at the other store are slightly smaller.
The bales that I buy run around 40-50 lbs and cost about $5. It is grown loacally in the summer and they get Canadian hay in the winter. They are timothy with some clover mixed in. I usually go through a bale every two weeks.