of course. How can a business succeed without any margins ? The point they are making is that the margins are ridiculously high that these stores charge. They are claiming to reduce those margins.
"Here is how a cheap mattress is marked up"
I browsed through their website. They don't claim to be a luxury mattress and their point is more about a reasonable mattress for a reasonable price. Of course there never is a limit for how much you can pay for anything. Think a $15000 Honda Civic vs $100,000 BMW 7 series.
I think you are being a little too harsh in your criticism even though trying to be constructive. It may not be all marketing as Amazon reviews are pretty good. And Yes, Amazon reviews are definitely worth it (being an amazon prime member who orders at least 10-15 things a month).