make sure that they are not made of toxic materials? after all, would you let your toddler chew on poisonous toys? of course not. then why would you let your dog do it?
at first it does seem like it would be better for your budget to buy cheap dog toys. but that is short term thinking. once you start having to pay vet bills because the cheap toys make your dog sick, you will wish you spent a few extra dollars for those dog toys made of natural materials, instead having to pay a few hundred dollars to the vet.
the trick is to know whether your dog is a chewer 