My vet charges $75 for an office visit, so we only go for his yearly and to get his sentinel. The mark-up isn't too bad. They tried to get me on trifexis last year when Sentinel was out (the vet didn't mention it, just the pharmacy guy). I actually drove the 20 minutes back and got heartguard because once I saw the potential side effects I was pissed. The vet didn't even talk to me about it, just assumed I would go with whatever. It is also the local emergency vet (open 24 hours) so I like his records being there. Of course, they screwed those up too (they had his rabies and DAAP lasting 4 years instead of 3).
If I had multiple dogs I would probably go elsewhere because it is so expensive.