First, I have to urge you to keep the males very far away from the female, since bunnies have been able to push cage bars closer and impregnate a female when you think there’s a couple of inches of space separating them. You have a high risk situation for pregnancy.
The neuter of males is less $ than the female spay, but if you did her first, that removes both the risk of a litter and of her getting cancer at an older age. Be aware that you need to keep them very separated for at least a month after any procedure. And the males will still be aggressive toward her and each other.
So if cost is your only issue, I would start by searching the internet and phone book for local shelters and rescues that take rabbits. Not to get rid of them, but to ask if they use a vet that does the procedures for their rabbits. You may find one that will perform a neuter, if not a spay, at a shelter, or get the name of a vet who works with them that you can call. Often, a vet doing those is very experienced, so good at the procedure, and may charge you less.
There’s also a financial service called Credit Care, and that is a credit card that allows you to get a medical procedure done, and pay back in payments with lower or no interest. Check it out. Many vets will also allow you to bill in payments as well. And many vets would give you a discounted rate if you have all three done with them, in quick succession.
Call around for other vets. Your prices are a bit on the steep side, so you might find a vet, under Exotics, that will do it for less. Check out the HRS vet finder that I believe is linked to a pinned post in Q&A forum that will find experienced vets by zip code to call. Even if you want one vet for illnesses, a speuter is so common with certain vets that you may find one a little further from home who is good, but less $, and you can get your medical care later on locally. I’d rather see you explore these options and have it done for one female, both males or (best scenario) all three. You will have a terrible time if she gets pregnant. Not worth the risk.