Hey JMS I respect that.
And while I am certain that it can happen as you describe it also happens positively quite often. Look here to this example:
https://www.goodingco.com/vehicle/1973-porsche-911-2-4-t-targa-2/
That car was assumed to go at or around estimate at the time, but it exceeded that figure by a large margin. If the cosigner had not been connected with the right people his result would not have been as lucrative. There are countless examples of the same when working with a premium auction house.
With that said, cars that may not offer that
something special may perform less dramatically ~ but for my cars, and the like minded - We generally come out ahead when working with the good auction houses.