You may even luck up on an unattractive apple tree at Walmart that got passed up throughout the spring. I did that several years ago on an old-fashioned Winesap which I was considering ordering off the internet. Just pruned it some to make it look better. Paid 12-$13. It’s one of my most consistent producing trees now.
What have seen from the big box stores is trees that are maybe properly labeled but with no rootstock information on the label. If that is okay with you buying it then it maybe a good deal. I was at Whole Foods a couple of years ago trying to find a particular item without having to buy it online and pay additional shipping. They actually had fruit trees there to buy. All they said was " apple" " peach" " plum" “cherry”. No description of what variety or size tree you were buying. Really odd to see.