I agree, it's crazy. Based upon the pics it really looks like nothing special but a small aluminum radiator.
If one were resourceful there must be something else that would work and fit. It could be a big risk on a customer's car because nothing about the inverter system is inexpensive and you'd look guilty if anything failed, even for unrelated reasons.
If I owned one I'd certainly try it on my own vehicle. A radiator is a radiator unless this has special check valves or a specific flow rate or something (doubtful).
Toyota's pricing here feels almost unethical, but they can argue supply and demand, etc
My customer will be happy just to get the vehicle back working properly, although I told him we'll have to see if the electric water pump was damaged-- apparently it's hard on them to run them dry.
If it were my own I would not pay $600 for a small radiator on general principle alone.
