Researchers for the University of Canberra have found that it costs roughly $500,000 to raise two children from birth until age 21. The amount varies depending on your income level. High income earners spend a lot more on education (presumably due to private school fees) whereas low income earners seem to spend a lot on recreation. Not sure if this amount include loss of income.
This research delivers no big surprises to me. I’d like someone to do a study which shows only what you need to spend to raise a happy, healthy child, which should be roughly the same across all income brackets.