Honey imported from China has been documented to be cut with high fructose corn syrup among other things. I'm sure there are a few less than honest folks who might try doing as you suggest. Caveat Emptor!
Fortunately, some honey is pretty distinctive - orange blossom, meadowfoam, berry honey, tupelo, and heather are just a few that you won't likely get mixed up with anything else. I'm not sure about apple blossom.
If you deal with reputable folks, you'll get good honey.
BeeFolks, who are great sponsors of this site, the Mazer Cup, and mead making in general have great honey. It isn't always cheap, but with them, you get what you pay for. You can find other good suppliers that people have dealt with mentioned in posts throughout the forums.
If you have a local producer, then you can meet them face to face and see how much they care about their product - you'll probably be able to tell what kind of quality you are getting (and you can learn a whole lot). If you find a good producer, be sure and post up to tell us about them - we all like to support good folks.