While I agree in principal, that you wouldn't want to support a puppy mill, no one here really knows about the origins of the particular dog you are interested in. The reality is, THAT puppy has to go somewhere. If nobody buys it, what do you suppose will happen?? My husband threatened me with a pomeranian, also from a pet store. I don't care for the breed, and said I was willing to agree to a Westhighland, or Cairn, terrier. The very next day, I started calling breeders and rescue organizations. I was one of the people who would NEVER, EVER buy a dog from a pet store. But guess what...there were 40 people ahead of me on the breeders list, which meant a wait of several years. Later that day, I found out that another pet store had ONE Westie. How could I think it was anything less than fate, when less than a day after committing to a breed, one miraculously appeared! We went to see her, and bought her immediately. I have absolutely NO regrets. She has been a part of our family for more than a year and a half, and I am thankful on a daily basis that I had the good sense to take her into our home. She is a delightful pet, with a perfect temperment.
Bottom line, that dog needs a home. Do what your heart tells you.