I don't know this person or her dogs, but have never seen an EM puppy from health tested parents for only $800. That's like dirt cheap pricing around here. You're looking at $2000 - $2500 for a conformationally correct (looks like a Mastiff is supposed to) puppy from fully health tested lines.
Every breeder I have had the pleasure of talking to are usually 2,000-2500. Some as high as 3500.
Just following up on this ... the going rate for dogs from reputable lines is $2000+ (with most being $2500-3500).
Also, note that some people may charge you (i) more for your pup but help you pay some/all of the health testing ... or ... (ii) less for your pup but require you to pay for most/all of the health testing.
Additionally, some breeders will require you to show your dog in conformation shows, an additional expense.
Some will require you to take your pup to puppy kindergarten and/or get a Canine Good Citizen award, an additional expense.
Etc.
Just because you write a check for $_______ to your breeder when you pick up your pup doesn't mean that's the ACTUAL cost of your pup ---- if you sign an agreement that obligates you to pay for ANY of these things, then you need to add these things to the cost of your pup.
And, lastly, if you get a dog with ZERO testing for hips / elbows for any of the dogs in their recent pedigree ... and ... you end up spending several thousand dollars of vet bills, you should probably add those costs to the price of your pup.
THAT SAID ---- THERE ARE MORE THAN A COUPLE OF BREEDERS WHO DO NOT TEST FOR HIPS/ELBOWS WHO HAVE PRODUCED MANY MANY MANY GREAT AND SOUND DOGS ... and ... THERE ARE MORE THAN A COUPLE OF BREEDERS WHO DO TEST FOR HIPS/ELBOWS AND STILL MANAGE TO PRODUCE A REASONABLE NUMBER OF PUPS WITH JOINT PROBLEMS.
Testing isn't a cure-all.