A 18-month-old child from a low-income household presents to the pediatric clinic with poor growth. On examination, the child shows **A** — marked wasting with loss of subcutaneous fat, visible ribs, and frail extremities. The weight is at the 2nd percentile and has crossed two major percentile lines downward on the WHO growth chart over the past 6 months. The mother reports she dilutes the infant formula with extra water to make it last longer. Which of the following is the MOST LIKELY primary mechanism of failure to thrive in this child?