@moto_man It’s not very useful sometimes to take a "logical" approach to "illogical" purchases. Emotions are intangible, and if we’re trying to make the math work, we’re going to be left scratching our heads.
Big receivers were the "big block Chevelles" of the day. Muscular, and "the brand" to own was, well, THE brand to own. Porche 911s were a different critter altogether. More refined, better all around performer, but didn’t have the "correct number of cylinders (8)" and didn’t come from the correct factory (Detriot). Not even on the radar for American muscle car enthusiasts.
Now more nostalgia. Tube amplifiers, although sonically superior, were priced out of range at the time, and were more complex. You needed a preamp, AND a tuner, AND more cables, AND more space. AND more money. The power ratiings were also lower, which to raw horsepower guys were not very appealing. And, yes,, a big receiver would play louder. So, the incidence of "big receivers" vs vacuum tube separates in the homes of the "average" consumer (whateve that is) was very high. So, the walk down memory lane to tube gear is a narrow path compared to mass appeal to "mainstream" big power receivers.
Your buddy bought the big Marantz because something drew him to it. I can’t tell. you what all those factors might have been (he owned one, a buddy owned one, he always wanted to own one, or ???) but I can say for certain that sound quality "bang for the buck" was not one of them.
Who’s to say what factors contribute to someone’s enjoyment of their music and the hardware that reproduces it? He could have spent $2k on a new bike, or tire/wheel upgrade for his car. He spent it on hifi gear. And, should make us smile.