Considering FUE on crown. How many grafts will I need for full coverage? (photos)

Photos cannot determine if you would be a good candidate for surgery.  You need an examination and the doctor needs to understand your goals, expectations, and future ongoing hair loss.

Thanks for the question. Based on your photos, the 2500-3000 grafts might be good opiton for you, but it would be wrong to say something for sure. You should see a board certified surgeon. You can then plan the process together and discuss the results. I wish you all the best. 

Crowns can be notorious for getting good coverage.  From your photos I would estimate between 2500-3000 FUE grafts to cover the area sufficiently.

A great first step would be an online consultation. Often you can submit photos to top hair restoration surgeons for a complimentary evaluation. This should help lead you in the right direction. Having multiple consultations with different doctors cannot hurt. 
Below are critical questions that you need answers to before moving forward with an FUE clinic. 1) Is your Doctor the person doing the FUE harvesting or is a Physician Assistant or technician doing the harvesting? 2) How long has your surgeon been doing FUE and FUE harvesting? 3) How many FUE cases does your doctor perform monthly? 4) If your doctor does both Strip and FUE, Does your doctor perform more strip cases then FUE cases monthly?

Thanks for your question. The vertex is a very important area for men as it is a classic early area of thinning - and no one wants a bald spot. In general, at least 600 grafts (Triple hair units) are needed for  even coverage. This being written, your vertex thinning is wide and you may need 1000 grafts. The area tends to be very receptive to Rogaine... not sure if you have tried this?  Best of luck from NYC.