FUE procedure 3000 - 5500 grafts. I have been told different numbers by different doctors. Opinions?

According to your picture, you have Norwood 6.
The donor area is the base to estimate the grafts needed.
In one session of FUE, the most grafts number implanted is 4000 grafts more than this number it will affect the donor area and the recipient area. the risk to have hairloss shock and damage the back side is high.
if the donor area is very dense than we estimate 3500-4000 grafts. the density on the frontal part will more than the back crown. There is a difference between the density and coverage.

Someone with your hair loss pattern may be perfectly happy with 1000 grafts, while others may not be happy even with over 3000 grafts.  You also have to realize one surgery may not be enough. To add to the confusion, straight black hair on fair skin results in a thinner appearing outcome then someone with curly blond hair on fair skin.  I hope you can appreciate there are many factors to your end result than just a "number" of grafts.Photos cannot determine if you would be a good candidate for surgery.  You need an examination and the doctor needs to understand your goals and expectations.
You need to have good communication with your doctor to understand what your end result will look like.

I use a formula to determine what is the safe number of FUE grafts that can be harvested in the lifetime of the patient and it ties to the donor density, see below