In the summer months I grow my own grass hay for fall/winter time, etc. Usually I don't get much more than half a bale, but it's still great! Really helps to cut costs and add more hay to the pile!
I feed my bunnies mostly only carrots, we've just started to get into buying nicer veggies & fruits for them, like parsley, etc. They do get salads sometimes, other than that their main treats are apples, orange, banana, lettuce, grass, etc. and often only a couple times a month, too. A bag of feed for 9 bunnies usually lasts a month or so....and a bale of hay probably two to three months, depending on size.
None of my bunnies have had to go to the vet for any emergencies (although really close with Magic these past couple days as he's gone through/is recovering from Gastric Stasis) We're hoping to get some of the girls spayed this fall/winter, and that will be a couple hundred or so.
Other than that, nothing else in which we really cut down the costs. Our bunnies are pretty cheap, hehe. Maybe costing at least $20 a month, $35-$40 on the months they need a new bag of food, litter, shavings, etc.
Emily