It's really hard to estimate the vet side of things. Food and such not so bad, but in my experience very high vet bills are not always the average experience. My last dog didn't cost me anything except annual checkups until the last 9 months of his life. Even then it wasn't terrible, just meds costs. Similar experience for other family members canine companions.
But when things go wrong... very expensive. There is pet medical insurance but I haven't decided if that's a good thing or if it's an expense full of loop holes that gets them out of paying.
I don't think I would recommend against a dog because of the potential for high vet bills. Same can be said for a car, having kids
etc. It's a factor to consider, and you should weigh the risks in a rescue or pound situation where you can't know the dog's history, but there are lots of good dog experiences out there where the majority of the money spent just goes into normal maintenance.
If you are just looking for primarily a home buddy, a cat is as
@lowfat said an easier recommendation. Although he's had lots of struggles with his current dudes, so one never knows. I'd say though a dog is 100% a larger commitment than a cat
@Shadowmeph
