Why pay so much?

They can exist. And I don’t want to bring up the $10k amplifier challenge by Richard Clarke, but 10s of thousands or people are yet to identify amplifiers with the same gain and same frequency response as to sounding different.

If you want .001% THD instead or .01% and a higher dampening factor to take it to 11? Fine.
But most people don’t care about taking it to 11 (Spinal Tap reference) and a $350 7 channel 1,000 watt rms factory direct amplifier can exist when a 6 channel car audio amplifier exists on 3rd party sites, so 2 people taking margins instead of 1 on the factory dirext, and cost to build margins, so if a car audio company with 3rd party sellers can sell 6 channel 1,000 watt RMS amplifiers for $200? I’m sure the factory direct audio world can do it, too. Especially since car amplifiers and home theater amplifiers are so similar.

The margins are what makes something a good deal or not to the buyer.  If a company takes 300% margins on speakers, then you get more bang for your buck as it's $400 on $100 to build instead of you paying 3,000% on $100 so it's $3,100 to you.  It's all the same product, it just equals more value with less margins, or  as the money isn't invisibly and magically going to the speaker building company or wire building company instead of your pocket.

Lower margins = cheaper prices, and more bang for your buck on the same product

My post was about the thread that mentioned actual amplifier model. I forgot details but it does exist. Again, it might have not been 5-channel but it was probably not mentioned as the topic was not in that direction.

So, chances are that what you want exist. If it does, why do you care about other things?

Huh, I guess I need to emphasize that there is a subtype of people who are not focusing on the "best deal" or "bang for the buck". They are more focused on the final product. I suspect that those who buy very expensive cables fall into this category.

In case you own a car, is it the best deal or best bang for the buck?