From your replies I understand you feel it's important for the kids to go to daycare even if you could find someone to babysit in your home for less than that. Fair enough. But it's not a black or white choice. You can keep the kids in the daycare for monday, wednesday, friday and have an in house sitter for the other two days for example. Or, if there's a family nearby you match with, watch your own children and theirs on tuesdays and let them do the same on thursdays or something like that. That will still give the kids plenty of time to build social skills and keep a good schedule, but at the same time free up some money. Or perhaps one, or both of you can change into 4 10 hour days. That'll free up a day to be a parent, saving on daycare again without losing the benefits of daycare.
The day care, mortgage and car payments make up by far the largest amount of costs so it makes sense to look at those first to save money.
Sonja, you articulated this quite nicely. I applaud the OP's commitment to his children and I also appreciate that his wife may want to work outside the home, so it's not strictly a decision based on the numbers.