Totally with you on this Kevin. I struggle to hear much, if any difference between compressors and EQ’s etc etc… and if I can hear a difference it’s usually right on the edge of perception - and certainly when it’s immersed in a complex mix featuring numerous other plugins it very quickly becomes irrelevant. It may be that some are just blessed with superior hearing but I also think it’s true that many perceive or imagine an improvement that is directly proportional to the amount of cash they just parted with (psychoacoustics). 
Not directly related Kevin, but you or anyone else may be interested… take a look at this interesting ranty ‘scam bust’ on the UAD “Voice of God” (VOG) plugin:
And yet you’ll find glowing reviews elsewhere.
There’s plenty of marketing hype and ‘Emporer’s New Clothes’ in the audio world - both around hardware and plugins. I for one use the stock Cubase plugins almost exclusively. They’re perfectly fine and do a perfectly adequate job IMO… and you’ve already paid for them! I rather suspect the improved mixes many seek will more likely come as a result of improving skill set rather than throwing money at some piece of hardware or plugin.
And that challenge you proposed to your friend… the blind test. Many years ago I recall reading articles about ‘golden-eared’ audiophiles either refusing to participate in such double-blind tests OR if they did, completely failing to identify the gear in question or observing (hearing) differences between the gear.