I think only a very few people do not consider finances when
planning a family. It is certainly one of the biggest considerations for me. I was gung ho for a third until a few months ago. Even though the expenses get disproportionately ridiculous when you go above the 2 kids "norm" (think house size, car size - try getting three car seats to fit in your average vehicle! - education savings, etc), I still think my biggest barrier to a third right now is... me. I already feel stretched to give both of my energetic boys the attention they need from me and balance that with a part-time workload. I just don't have the energy to deal with another baby right now, let alone the toddler that baby will grow into!
Husband and I are very much on the fence about baby #3. If finances were not a consideration (as in I would be able to take care of everything from house reno costs to vehicle change to a nanny service so that I could still have about 20 hours a week of professional time), then I would probably go for it. Probably. Maybe. Hmmm. Get back to you all on that in a few more months?
On this talk of benefits, I have to say that one of my greatest frustrations is a LACK of national subsidized childcare in our country. How many couples do I know that are in our position: childcare for two kids pretty much wiped out one income - we cannot AFFORD to keep our fulltime jobs. I am fortunate that my husband's job allows me to choose to stay home and work on call (so that I don't go crazy and so that I can maintain a toe in the door in my field). But I love working and it is a big part of who I am. I wish I had more options for safe, decent childcare. And having so many professionals basically blocked out of our fields while we raise toddlers isn't great for our economy, either. I think we should be a lot more creative and design a system for working parents that allows for choice. I think it can be done.