This thread is getting interesting... lol
but I have to disagree with this statement here.. and a few others.
First off..I'm a disabled vet with very little disposable income. I have a bike with Di2. I'm simply resourceful.
Secondly, i know PLENTY of people with high disposable income that are extremely wasteful and irresponsible with their money. I know far more folks with low disposable income that are able to stretch said income as far as humanly possible. They have to maximize what little they have to survive.

Lastly, this thread has gone WAY off topic. We somehow turned this into an argument about wealth? Look out on the web, you can buy new/used bikes with di2 for very reasonable prices. But, since we're knee deep into this...I don't think di2 is a sign of 'wealth'. Rather, I would say that if you ride a $8k+ bike with top shelf components...and you're not on a race team and just ride on your own or casually with the LBS... that.. would be more of a sign of wealth or high disposable income. At least more so than having di2 on your bike.

Oldnslow got it right, it's about desire and what you value when you ride. Di2 isn't necessary, some folks just prefer the feel of it. If you say it's excessive.. the same could be said about frame material... You could say carbon or Ti.. heck even 'new steel'... is unnecessary..aluminum is fine.