The cost of detecting and treating flat head syndrome can easily be estimated as hundreds of million every year. There are 4M births per year in the US . Almost half of newborns demonstrate some degree of flat head in the first few weeks , Lets say half of them do an extra visit with their pediatrician for this concern (~$150/visit). An estimated 20% still have it at 4 months of age  and if they are referred to pediatric neurosurgeons or physical therapists, this causes additional $250/ neurosurgeon visit, and $150/ avoidable PT visit. An estimated 1-3% go through helmet therapy, $2-5k. Hence the total cost is [$150*0.25 + ($250+$150)*0.10 +($5000)*0.01]*4M=$510M
Many babies do multiple physical therapy visits for treatment of torticollis which is tightly correlated with flat head syndrome; and many parents buy mattresses, pillows, and other preventive or treatment products that adds to the above cost.
 Martin JA, Hamilton BE, Osterman MJ, Driscoll AK, Drake P (2016): Births: Final data for 2016.
 Mawji A, Vollman AR, Hatfield J, McNeil DA, Sauvé R. (2013): The incidence of positional plagiocephaly: a cohort study. Pediatrics, Aug 1;132(2):298-304.
 Carl Cummings, Positional plagiocephaly. Paediatr Child Health 2011;16(8):493-94. Link: https://www.cps.ca/en/documents/position/positional-plagiocephaly#ref1.