Utterly unacceptable!
When l bought mine l was not asked to pay any deposit, whatsoever. Sea trial or not, l would not have paid a brass razoo, anyway. (the dealer, during the sea trial melted the pong box by not turning on the sea cock - so what about the ten% then?)
I thought Eddie Obeid was Mr Tenpercent?
The 'suitable buyer' requirement might be acceptable if the subject is of historical interest. But even then...???