We spent 60K last year, so 5K per month, for everything.
Pay off the house, and we're down to 48K or 4K per month.
That includes a fair bit of travel (nice!), our clothing budget would drop (yay! no more fancy work clothes), and I'd have a bit more time to shop/cook more strategically, so I'd wager I could get it down another 500/month. I'm keeping our medical expenses in there b.c. I really do think those will go UP not down.
So with a paid-off house and skepticism about health care, call it 3.5K-4K a month for a rich, fun life for us (and our pooch)!