If we're just saying that the rental companies can charge $900 for the TV because that's what people are willing to pay, the same applies to paying $450 for bra

If we're just saying that the rental companies can charge $900 for the TV because that's what people are willing to pay, the same applies to paying $450 for bracket installation. In a competitive environment, you should expect the price to be close to the marginal cost of providing the service. The marginal equipment cost for providing a TV is the cost of the TV divided the number of events you expect it to last through. This doesn't change if you have spares. To get close to $900 for a $500 TV, you either need extremely high overhead and labor costs or TVs that break a little more than halfway through the rental. If a TV can generally survive 30 days of use, equipment costs only justify $50 of the bill for a 3-day rental. I don't see how you would get anywhere near $900 from there.