How tall were his parents?
What kind of illness did he have? Most dogs will rebound from common illnesses.
What you paid is all relative... I've run into people who have paid more for their puppy mill Lab from the internet than most people pay for a well-bred, well-pedigreed, Lab from a reputable breeder.
Even if he is from a great breeder and you paid top dollar, there's no guarantee that he will be the perfect standard. I wanted a "normal-sized" Lab this time, as I was looking for a dog that was a little more manageable for what I wanted to do, so went with a litter where the mom was normal Lab sized and the dad was at the smaller end of the standard. I ended up with a 25 1/2 inch 100 lb Lab that shadows each of his siblings as well as his parents. Apparently, he takes after his paternal grandfather in size.