while I do believe the market dictates the value (if people will pay $800 for a bottle it's worth $800) I'm also a firm believer in diminishing returns on something like this, ie there is no way a $900 pour is 13x as good as a $70 pour (not that things like this can be quantified). I think it's obvious you are paying for the uniqueness and bragging rights with these ultra luxury items.
I could afford it but I am too cheap ... most I have paid for a bottle is $90. I've bought 100s vinyl records that cost over $90, but zero over $800, so you know where my priorities and limits lay