From what I can find you are looking at 500 dollars maybe a little less if you talk directly to the breeder...www.bulldogbreeds.com
How Much Do American Bulldogs Cost?
I have 3 and I got them all for free if you can you should save one I even saved 1 of mine from a dog fighter and he is a great dog I save lots of dogs and my bulldog get along with other animals and my 2 kids great
If you are buying from a reputable breeder, you're looking at anywhere from $200-$600... And that also depends on the bloodline, etc. Try looking at your local Bulldog rescue first though- there are LOTS of homeless AB's that need homes. :)
I have been looking at AB's for the past two months they are being sold anywhere from $500 - $2000. With most in the $800-$1000 range. You may be able to find them for a bit less if you want as a pet and do not intend to breed.
On average they're about $800+