As for the argument, "you have two incomes, use them to buy time", well, it depends on the context.I think the argument about having a lot of income in a dual academic couple primarily applies to both adults living in the same household. I should have specified. But there are a few words to be said about a 2 (+ epsilon) body problem.
If the two people in the couple live appart, this is not so realistic, because these two people have to maintain two households and commute to see each other from time to time. In fact, maybe you can add some comments to how you do it, I never done the long distance since after Toddler was born.
If everybody lives under the same roof, this is more possible, but still depends. In Canada professor salaries are low and pay a lot of taxes, so that doesn't apply to us: we can afford the regular daycare, but we can't afford a nanny, for instance.
However, I've seen couples make cross country commuting work on dual graduate student salaries (albeit without a child.) What they have sacrificed is having anything in terms of savings. Also, the particular people in mind all worked outside of academia for several years before entering graduate school, so they started eating into their savings from that period of their lives.
Some things I've learned about long distance relationship finances:
1) Buy tickets long in advance. I've been bitten in the pocketbook because I've tried to buy tickets for the entire term starting at the beginning of the term. All but the last few weeks of the term were more expensive than they had to be if I had been on the ball. Frequent flier programs, credit cards that earn miles, AAA discounts all help.
2) Live within your graduate student means. Epsilon was born a few months after I stopped being a graduate student. Therefore, we never got out of the habit of living like graduate students. All of the extra money from first my salary, and then my partner's has gone either into childcare, savings, commuting or a second rent.
3) All time saving devices are not created equal. For instance, there are different types of daycare that come at different prices. Nannies and large daycare centers that care for dozens of children at several different age groups tend to be more expensive than day cares run out of people's homes. Depending on what you want and need out of day care, the latter may be sufficient. We are saving about $900/mo by choosing the latter option.
Similarly, buying time on food prep does not have to mean eating out all the time, which breaks both my fiscal and caloric budget. Take a second look at the deli section and frozen foods section of your local grocery stores for partially prepared foods. We found, on warm days that we could combine Epsilon's walk (back when he still enjoyed going for a stroll in a stroller) with a run to the local grocery store for a loaf of fresh bread and soup, cheese, fruit and tomatoes. This was a much more enjoyable dinner to eat on the lawn than going out to the local upscale burger joint. Sometimes there are small catering businesses that have meal plans, where they deliver X meals/week, delivered to your house.
In January, when our 2-body problem gets bad again, I'm planning on hiring someone to come by the house once a week for a few hours to clean. As long as I can control the amount of mess that Epsilon and I make, we can get by with just a few hours a week. Figure out where the steep changes in the price points are, and see if you can work within those ranges.
4) Utilize your housing space. If you are about to move, or if you have an extra room that is under utilized, consider rearranging space in your house to have a house mate. When we moved to this job, we got a 2 bedroom house, with the knowledge that Epsilon would probably want his own bedroom by the time we had to move again. In the mean while, we rented the spare room out to an acquaintance with the agreement that part of her rent would be paid in childcare. This solved the problem of not having outside the home child care for Epsilon during the first several months of his life. After she moved out, and while Epsilon was living with my partner, we rented the spare room out as a temporary sublet. This was also a solution to my unease of leaving the house completely empty for weeks at a time when I was away. If you are in an urban area, Craigslist is a great resource for finding matches.
5) Be creative. Epsilon is a very early riser. At one point, I paid the aforementioned house mate to come by and take him in the mornings so I could sleep in until the sun had risen.
The ironic fact about our budgeting is that the biggest crunches we've felt the for paying our credit cards has been when our respective universities budget offices haven't refunded us for our conference travel. It's really hard to hold a buffer of a few thousand dollars in the bank account for several months because the university is swamped with reimbursement.