I've been raising meat rabbits exclusively on good quality hay and oats for a couple years. The local Amish here do the same as well. As for 50% mortality rate, it seems absurd to me. I've changed pellet fed rabbits over to hay/grain/fresh produce without issue (quicker than I should have as well).
I've calculated one square bale will feed one adult doe for roughly 30-34 days. That's 13 cents a day. Oats I free choice, but it's around a penny a day... so, 14 cents a day roughly.
