Maintaining a Mastiff is expensive. You need a specious home for them, good food, vet, training, toys to keep him healthy and happy. As they grow in age several health problem occurs, so vet bills can be very high.
They can give birth to 10 to 12 puppies at a time. There is a record of giving birth to 24 puppies in England. Caring for a pregnant Mastiff and her puppies is not only stressful but also expensive.