I have seen that for sale a couple of times before. At that price he doesn't want to sell it, he just wants to show off what he did.
That's a kids bed, I sleep in a California King. The Silicon valley types tend to spend money on odd things for their kids rooms. One house here has a recreation of a Star Wars moisture farm and the kids live in it. Parents work at Pixar.
I have the Sealy posturepedic. It is a real mattress. The only thing I don't like is that due to the pillow top you can't flip it over, only turn it around. At 8 years old, I am looking into a replacement. Most beds nowadays are too soft though. My daughter has the CA King memory foam, that thing is so soft it is already giving her husband back problems (he is a plumber and healthy so his back should be in good shape). The best bed I ever had was a closed cell water bed back in the late 70's. It was soft to movement, but couldn't compress. I have never seen another one like it.