What makes an expensive speaker expensive

Paper cones can sound very good, but that does not change the fact that they are in total break-up at nearly all frequencies and therefore not an accurate diaphragm to excite the air in the room. Subsequently, the ear drum can't preserve an instrument's waveform. Most people think Bose speakers sound great and are totally adequate, but those who listen know they are not

It's a personal thing and I get that.  I won't be able to change your mind and that's cool. It's what makes the hobby part fun.  Most of the major and respected designers are working hard finding newer materials to make a pure pistonic moving driver.  

no speakers can be worth 50k.

any speaker over 25k are overpriced

I personally can and will never be able to afford a speaker over 25K, however making that statement that nothing is worth it is dead wrong.  It's proven to be wrong as we live in a society where folks control the market.  Plenty of folks are purchasing these and feel they are worth it, so they must be.  Maybe to you they are overpriced and maybe to you over 50k isn't worth it, but the market sure thinks they are and personally I am happy as the trickle down has helped speakers in MY price range of under 15k sound THAT much better.  

This is a discussion as to why speakers cost what they do not if they are worth it or not.  

Cost is what the market will allow. I've heard several speakers that are over 50K and if I had the money I would buy them. 

I would tend to agree with ricred1.  Some folks may not be in the US and understand the free market system though.  I full understand that part of the equation, but I'd think if you were on a board like this, you would understand it.