Compared to kids? My dog is almost 11 and he has been rather inexpensive, especially compared to kids I think. Getting the initial wellness shots was the worst financially, other than that it costs about $30-40 every month and a half to feed him and his brother (my fiancee's dog who used to be super picky but seems to want to do anything Buster does so he now eats Buster's food) and then rabies shots every 3ish years which are about $20. Though, to be fair, perhaps I've gotten rather lucky with him, I've never taken him to regular wellness checkups (they make them mandatory when he gets his rabies shots, though I would opt out if I could because they are the most expensive part of the visit) like a lot of dog owners do and he has never had any health issues except his hips are getting bad with age. I treat my dog like I treat myself: If something really seems wrong then we will go to the doctor, but until then we just live life and deal with the bumps, bruises, aches, and pains as they come. I haven't had a physical or wellness check of any sort since I turned 18 and probably since before that because my dad was much the same way. I haven't been to a dentist in a longer period of time but my teeth are seemingly fine, all straight and my wisdom teeth have mostly come in over time and no issues. I know that I couldn't take such an approach with a kid, but it's in my nature to do so, I'd just end up giving them Tylenol whenever they felt sick and Neosporin if they break a bone or something
I've always felt that mutts are stronger and smarter than purebred dogs though, so perhaps that's part of why he has been such a good dog. Got him from the pound when he was a puppy and he's a lab mixed with pit and probably a couple other things.