Since your hair loss is very minimal, I would recommend you continue the finasteride and possibly look into topical solutions such as minoxidil and possible at home laser therapies. See if you can over time get some density back in the crown. If the thinning bothers you so much that you cannot wait, then FUE would be acceptable to transplant in the thinning region. However, it would always be best to get advice from a qualified hair restoration surgeon that can examine your scalp in person and give you recommendations.
Your hair loss is still minimal that is why keep up with your medications.You may also start using Minoxidil as a second treatment for the crown area balding.
You need to understand what is possible and what is not
500 to 1000 grafts that you were told may be acceptable. However it may not give you the fullness you once had or give you a no-see-through effect. Aside from possible shock hair loss and continued hair loss, you need a lot to make an impact on a minimally thinning area. Example: Adding 10 hairs in an area that has 100 hairs will not make an impact versus adding 10 hairs in an area that has 20 hairs. Using drugs (Propecia or Rogaine) may give you a better result than surgery with less risk. Example: Drugs such as Propecia or Rogaine can make those 100 hairs thicker while growing additional hairs in between.
Finally (as I always advocate) you need an examination and a diagnosis before deciding on a treatment plan.
34 with very mild crown balding
The best answer to that question is to try medications and not a hair transplant. Your hair loss is minimal and medications like minoxidil and propecia when taken in combination have an excellent chance of your growing your hair without any transplant. That has to be better than surgery. IF you insist on a hair transplant, than the quote give to sound reasonable.
Alternatively, you cah have scalpmicropigmentation which is almost a guaranteed, non-surgical cosmetic solution. Wee thinning hair in our web link below and you will see miracles in making a thin crown disappear without surgery, but medications for a year is still a better option.
Hair transplant in the crown
From looking at your picture, you have some thinning in the crown area which would make you a good candidate for medical treatment. Since you are on propecia, I would recommend rogaine and vitamins as well. However,if you really want to do surgery to add density in the crown area, I recommend 1000 grafts, but I do recommend that you stay on the medical treatment option to prevent future hair loss.
Hair transplant - when is it too thick?
With such a high starting density, there's is a high chance you wouldn't get much improvement and a small chance you'd actually look worse as so many hairs might potentially be damaged.
There's a real risk with operating with such high density.
Hair transplants work best when the density drops below a certain level
Density of a transplant can get you to 90-95% of normal and you are about that now. I am not sure you would gain much.