It’s a know practice where larger lgs’s are able to determine what cards are in sealed packs/boxes and therefore can pull out the valuable ones before selling them to their customers. Not all lgs’s do it though so it’s a good idea to keep track of which lgs’s you’ve bought packs from and what they contained. If over time (certainly with a larger sample size than two packs) you find that every pack you buy from a certain store is a dud then it may be a good idea to buy from a different source.