It is broken down in terms of an hourly rate because trading labor for a reduced expenditure gives a frame of reference that most people can understand. For instance, if your landlord or mortgage company told you if you do 5 minutes of work and received a reduction of $100 on your mortgage/rent each month, showing the equivalent hourly rate of $1,200 is useful. It’s not that they hand you $100 directly, but if your payment went from $1,000 to $900, it effectively produces the same result. It could involve exchanging money, but it doesn’t help from a practical level. If a woman accepted, she could hand the daughter $1,200, and the daughter could immediately hand her $600 back, but it’s mathematically the same as the woman handing the daughter $600.