14 CONNECT 15 TWEET LINKEDIN 1 COMMENT EMAIL MORE. Parents know that children cost a lot of money, but most don't realize how much. An annual study by the U.S. Department of Agriculture pegs the total average expense from birth to age 18 at around $245,300 for a kid born in 2013, equal to about $13,600 per year.HOENIX -- An annual study by the U.S. Department of Agriculture pegs the total average expense from birth to age 18 at around $245,300 for a kid born in 2013, equal to about $13,600 per year. Post to Facebook.