What should it cost to replace all 4 ball joints? on 1999 Mercury Mountaineer

My ball joints squeak and need to be replaced.

Asked by for the 1999 Mercury Mountaineer
Assuming is 4wd then the estimator calls for $360 to $580 for lower ball joints and will need to add in cost of upper ball joints and a little more labor for the uppers since will have alot of same components tore down and some labor is duplicated. It also depends on what the going labor rate is in your area.
The Mountineer is all wheel drive, Any difference for replacing all 4 ball joints?
That is same as 4wd.