Hmmmm... that's a tough question. Our son started preschool 1 day a week when he was 3. When he was 4 he was going 2 days a week. At 5, he went 3 days a week. It worked out well for us, but obviously he was at home quite often.
The place we went allowed cloth diapers, and at 3 he was eating regular food. The preschool was pretty amazing and had it's own garden and cooked these great vegan meals for the kids.
The cost was $55 per day, so at 3 days a week, it was $690 per month (not sure about the math there, but that was the price). That was a full day from drop off (anytime between 8 and 9 am) until 4:00pm (with a nap from 1 until 3 or 3:30). The only thing we provided was one set of clothes (and they had extras just in case).
For us, it was more about getting our son used to being in a new place and eventually preparing him for regular school. If we hadn't found the perfect place, we would have kept him at home.
Anyway, not sure if that helps you at all... I'm not an expert on daycare, but it sounds like the cost might be typical. I have some friends that hire a live-in nanny and then they split the nanny between 2 families. So, the nanny takes care of 4 kids during the day (2 from each family). You can also hire someone to come to your house, which would take the stress out of morning routines and extra clothes, etc. out of the mix. If you had another child come to your house, you could split the cost with someone else. Technically, the extra clothes, formula and diapers is not a surplus, as you would be using those things at home if your child wasn't in daycare.
There might also be a stay at home mom/dad that you know (and trust!) that might enjoy taking care of your child during the day, along with their own child/children. They might welcome the extra cash! This is where having a community of friends can really help you.
Finally, I would look into seeing if you can accommodate some kind of flexible schedule, if possible. Sounds like it isn't possible, but maybe even working one day a week from home, or staying home one day and working a weekend day (when your spouse is at home) might help. Or possibly working a half day on certain days... there may be some options here.
Obviously the most important thing is having your child in a safe place that you feel comfortable with. Think outside the box and see what other options are available. You just might find something!