store or garage?

Do you buy the strollers, high chair, walker, jumperoo etcs...at the store or at garage sales? Is my first baby and I want buy it at the stores but my boyfriend's ex wife tells him to buy it at garage or flea market. She complained to him that why buy expensive at the store if not going use so long. I don't know why she is getting involve in my baby life, she has no right and is none of her business.  But what would you do?