I think the most expensive was the Phoenix Gold MPH-6300 at $99,000.00. Only one was produced and it was never sold.
I think the "Punch 45" really set the mark back in the day (yes, I'm that old, 38) for the mass produced amp as that was pretty much the only amp other than Orion used in the 50 watts and under bracket for IASCA. Then the "Punch 150" came out, then I remember the "Power 600" that Mark Fukuda used as for Rockford goes.
I also think the Soundstream Ref 705s and the Macs were very impressive in the mid 90's. Any one remember the Butler Tube Amps that were featured in CA&E in Michale Anthony's car? I tried to google it but had no luck.