Of course $20k is not essential for enjoyment. I'd say $100k minimum. I mean seriously, why would someone spend $100k or $200k on a system if it wasn't worth it?
calvinj, I think to suggest that people STFU in a forum discussing high end audio, or anything, for that matter is a little ironic. We're here to share opinions after all. I agree with you that if someone wants to spend large amounts of money for incremental differences that this their option and if it makes them happy then that is fantastic.
But we all probably have that point in which the skeptic lurking inside all of us comes out. The guy who has spent $100k on a system is going to be a tad suspicious that the guy who spent $485K on used speakers (they were listed on this site not long ago) is probably a little daft.
I also think the two ends of the spectrum are about the same: People who spend less thinking that people who spend more are doing it for reasons that don't warrant the expenditure verses people who spend more assuming that people who spend less are either settling for poor quality or just don't know the difference.
Finally, I do not believe that it is true that every additional dollar buys you a subjective or objective benefit. I think it is true up to large sums but there comes a point in most hobbies at which that extra dollar does not buy a dollars worth of benefit and in some cases will buy you less.