I can see spending:

1.5K/month on insurance (car, homeowners, health, etc.)
0.5K utilities (electric, gas, etc)
0.5K groceries and gas
0.5K medical

That is $3K without any home repairs, eating out, entertainment, travel, clothes, car repairs/registration, taxes.

Any couple doing it under $6K is doing things very efficiently.

I think somewhere around $8K is more realistic.

I know others are making do with less but they must have a small house, grow some of their food, have a single car, minimum insurance, etc.
We aren't big spenders with clothes, jewelry, cars, etc. And we have been doing well with various restaurant email programs to save a bunch.

Fortunately despite the spending and a conservative portfolio, the spending hasn't caused it to go down over the couple of years of retirement.

Rich