I think this applies to all popular breeds, not just labradoodles, but I suspect it's because they see other puppies being sold at a good price and figure they will be able to charge the same. Unless you are involved in your breed (and relatively few people who breed from their pets are), then how do you decide what to sell your puppy for? You look at what other people are selling theirs for....and the internet advertising sites are readily accessible to most.