I expect my spending to be about the same when ER'ed.
I'm FIREd and on April 1st will be scaling back to a much reduced workload (PT with a new employer). I expect my earned income to be about 33% of my former earned income.
Taxes (Fed, State, Medicare, SS, SDI) were about 38% of earned income in 2007, and were such a large expense that I spent more on those taxes than I spent on myself...Please reminded me, who was I working for?
The only expense line that will increase dramatically is COBRA medical insurance, which will be almost $500 per month post tax, as compared to about $32 per month pre tax. Maybe I'll be with my new employer long enough to qualify for their basic medical, but in any case, ERing is worth paying for my own health care...
One additional "expense" that may go away, depending on circumstances, are contributions for retirement savings. No guarantees on this one, but I'm hoping to increase my IRA's earnings through better investing (something I'm trained in) by more than the $20K contribution (and employer-match) I used to make to my 401(k).
So, taxes and 401(k) contributions were about 50% of earned income for me in 2007. Way more than I spent on myself. Sorry folks, but once ER'ed, I will not be pulling the "ship of state" as much as I used to.