Mandy,
My husband and I were ready for the next one at different times. With baby #1 and #3, I was ready and had to wait for my husband. With baby #2 and #4, he was ready before I was.
I would say the best thing to do is sit down and talk with him about why...but not in a pushy interogation kind of way. Just a "this is important to me and if you don't want another child, I at least want to know why so I can understand your choice." Find out if it is a resolvable situation or at least if it is a "not now" or "not ever" when he says no.
It may have something to do with the current economy. Men (at least the ones I know) have this strong "protector / provider" instinct and often get worried about being able to fulfill their rolls. In regards to being able to afford another one, I personally think that is overplayed in our society. Sure, we should be responsible and not have children that our extended family or government will have to provide for. But that is so often not the case. Children don't need expensive toys or elaborate birthday parties or big vacations. In many cases, (as you pointed out) staying home is more economical than day care.
In our family's case, we cut a lot of corners. Second hand and hand-me-down clothes, coupons, cooking at home from scratch instead of eating out, sack lunches for husband and kids; no sports, extra curricular activities or lessons until age 6...then it is one activity for one season per year. Birthday parties consist of a few friends over to our house to play games, open presents, and eat homemade cake. We only buy our kids toys on Christmas and birthdays, and even then we only spend $40-75 per kid per holiday. We swap babysitting with other couples to save money. We pay cash for everything but our house and keep our cars until we can pay cash for a newer one. Our children have conspicuously less than their peers, yet the most frequent comment I hear about my children is how happy, confident and well behaved they all are.
I hope your husband comes around. Maybe he will; who knows?
Good luck,
S.