If you are looking for a boxer puppy for less than $200, your best option is to adopt, as boxers typically sell for $400 to over $2000. As of 2015, boxer puppies are available on PuppyFind.com for as low as $300 each.
There are agencies across the country with puppies in need of good homes, and many of these puppies are boxers or boxer mixed breeds. PetFinder.com and AdoptaPet.com are great resources for finding boxer puppies and dogs to adopt. If you are looking for a purebred dog, the American Kennel Club strongly suggests going through a registered and reputable dealer, and it provides listings of breeders with boxer puppies for sale.