Is positive reinforcement why things are sounding better?

I bought a pair of NOS Mullard’s for my tube DAC that cost half what I paid for the DAC. I swap them out from time to time with some much cheaper NOS Telefunken Diamond mark’s.

The Mullard’s sound significantly better to me.

And the Tele’s sound way better than the stock new Sovtek’s the DAC came with.

Sometimes you get what you pay for.

I have Tube Rolled on a few occasions, where there has been a Selection of Valve Pairs to be evaluated. 

Tube Rolling is a Two Edge Sword, as change to an end sound, can be noticeably discernable.

The change can stimulate a reaction, but does not necessarily create a betterment in sound for the end user, but a difference only. 

There are Tubes when demo'd as a type from a selection of types. that are capable of making a very good impression.

Most demo's I have been party to, have been carried out as a group in attendance. Within the group, there is not always a unanimous agreement, on what is the better tube. 

With the differences of assessments known, it strongly suggests that recommendation may not be ideal for a end user. 

"Soundproof Listening Room." Is that a Demetri Martin line? It seems to me that a soundproof listening room would be absolutely the worst kind.  Also, don't people notice if a new thing just sucks? Regardless of the cost...if it's not good (or maybe better), no amount of expense is gonna save it.

Confirmation biases has nothing to do with "lying to ourself" in particular or specifically

Yes, it does, obviously.

I walk into a certain big box store with a special high end audio room named after a tree in my front yard, I see some big name audiophile gear with impressive looking drivers and amps with big blue meters.  I’m in a large rectangular room lined with speakers against the wall and a bare tile floor.  I even see a pair of ML speakers pushed against the wall behind me.  The salesman puts on some music.  It sounds like a big boombox.  The music is bleak and uninspiring.  I’m dying just to move the speakers out from the wall.  But If I am a young, impressionable and budding audiophile then my conclusion is this 6 figure gear is so not worth the money.  I come to these forums and expound on my displeasure and distrust in the high end hifi community.  Everything is either snake oil or confirmation bias.  This so called hifi sound is a myth.

We have so few audio stores left but at least the few that I have been in have good set-ups.  Back a few decades, more audio stores than not had poor set-up.  Only a few stores had a room with a high end set up to showcase one system vs. rooms with gear wrapped around the walls.  But when you walk into a room with a good high end set up, be it a store or in someone’s home, you will know it.