I know quite a few people... there's a breeder nearby, so there are a lot at the local dog park and I've spoken both with her and other owners on several occasions.
The expense (more so than other bred dogs) is the double surgery bulldogs require
1) Caesarean delivery
2) Surgical removal of the puppy's tail from it's anus (many to most bulldogs are born with the tail inside their rectum. Sometimes the breeder has this done by their vet, sometimes it's done after adoption).
In our area pups run from about ###-###-####. The upper end are showdogs and dogs who have their tails perforating their rectum or large colon requiring more complicated surgery to fix the tears, or drain the cysts that formed in utero, and repair the intestine wall. Since that surgery is about $1500... that's what bumps up the price.
You'll have more luck finding a 1yo bulldog in shelters, from people who don't understand the breed (needing to clean the folds and tail daily) and have gotten sick of the vet bills from infections when they don't. ALSO check breeder pages for older dogs, though. Because all reputable breeders insist on having any puppies/dogs returned to THEM instead of rehomed by the owner. The cost on an older/returned dog is usually identical to shelter costs.... apx 200-400