If you can get accepted to DO school as a high schooler, you have a very good shot of getting into med school and an extremely good shot of getting into DO school at the end of college. These programs exist to get students like you who they think they won’t be able to get later on.
Going DO will probably close doors for you with regard to residency and that will cost you way more in the long run than a 4th year of undergrad.
Personally, I also think shaving a year of undergrad hurts your med school performance. It certainly appears that way for he 6 year programs.
The cost difference between a career in plastics, ortho or neurosurg vs gen surg is orders of magnitude more than one or two years of undergrad.