This is not how you compare gear prices, besides quality and the other obvious factors,there are two major factors you need to consider when making such a comparison.
1-Price per Terahash
2-Watts per Terahash
Now depending on a few factors , power consumption in many cases is the most important factor and based on that, and assuming the S17E does 64th at 2880w i see no reason why it shouldn't be selling for 3.5k or even 4k despite the fact that the M20s does sell for a lot cheaper, those 500w difference are worth a lot to many people , and to be honest 64th at 2880w is a freaking beast, I doubt any other company will get to that efficiency by year end.
Another reason is that to me, bitmain in the mining industry is like Apple in the mobile phone industry, they always get away with selling over priced products just because of their brand name.
I think my 1 liner resonates with point #1 in your reply. The M20S has a higher hash rate and a lower price than what we speculated the the S17E price would be. Is 4TH/s @ ~500 watts worth it? Probably not for most, but it also hasnt been reviewed yet either. So there is a chance that gap can be closed a bit.
I agree with you that its a beast with those stats. Bitmain was able get away with top dollar because nobody was able to get close to them in terms of #1 & #2 in your post. But I think MicroBT will be a formidable competitor and I think they have demonstrated that with the M10S & M20S. As long as they remain competitors, we all win.