Apple Store New York LLC pays Apple Spare Parts Cayman Islands Ltd $500 for a genuine Apple screen glass and does the repair, including the cost of wages etc, for $321. Thereby making a tax deductible loss.
Your local back street repair person buys the screen glass for about $5 including shipping from Ali Express and does the repair for $80. The $75 margin allows them to cover their costs and make a reasonable living out of it.