Imagine going to a car dealer for a look see and test drive and being told, "Nah, it’s gonna cost you to test drive this rust bucket."
Not exactly that, but something parallel to that happened to me. I wanted to test drive a Mitsubishi (roughly $30 000 or 40 000 car at that time, I do not remember anymore). Dealer asked for $5000 deposit before test drive he would be present at anyway. So I have never driven a Mitsubishi.
Speaking of judging the seriousness that the dealer from our amplifier story is talking about, I was very serious about buying that car on the spot. Now, the difference is that it was a new car and these are old amplifiers.