I've been a working mom and a stay at home mom. (When my youngest goes off to college in the coming year, I'll finally be an empty nester, yikes!)
I was well established in my career when I had my first child - I remember paying my student loan off the same month I gave birth! (Then the money went to diapers, LOL!)
I worked until we started moving around for my husband's career. I also got in the minimum (alot more) than 40 quarters for my social security and medicare. I believe that's SO important.
Younger moms don't necessarily get far up enough in their careers to make enough money to be able to have enough left over after paying into social security, medicare, health and other insurance, etc. and pay for childcare. I was offered a job with my daycare making the same as the director, which was decent money, but I would not have had retirement money and other perks, so I didn't change careers. As it was, I was able to take time off during the day to take my son to speech therapy twice a week because I was the manager and had many years of tenure - I would not have done this at a new job, even being the assistant director. (It's different when you have hired the people under you - all the teachers at my children's daycare would have been her hires and I wouldn't have asked it of her...)
I feel that I had a lot of quality time with my children while I was working. I was organized about my time and had a good schedule with them. It worked well. I was able to build up my retirement and get good experience and life learning skills by working. My children know that I worked, too.
After I stopped working, they had me to come home to once they started elementary school. I actually feel that that was better for them. I was able to manage the house better and help them more as a SAHM than when they were really little. And they are in school for many years longer than when they are really little...
I'm glad that I did both. Working now in a full time job doesn't make sense in our financial situation - I substitute teach because I like it, and I do a lot of charity work. I'm glad that I can - someone needs to do charity work. It's such a worthwhile thing to make a difference in peoples' lives. And it's good for children to see their parents 'give back', so to speak.
I guess what I'm trying to say is that there are reasons to work and reasons to stay at home, and one can't just put dollars and cents alone into the decision, especially in the short term.