Time. Once the basics are taken care of (food, shelter, medical care), time is a luxury. None of it matters if you are not here. The one thing money can't buy (although that's not true because the wealthy live longer than the poor), is time.

So, when it comes to work--working at something you enjoy is a luxury, because time spent at work is your time.

Another luxury...family. Maybe more than time, because most of us would give up our time for family if necessary.