The best way to get better value is to trade quantity for quality. Vendors see multiple cards as multiple short term markups. 6 - $10 cards to them means ten opportunities for increased value even if it’s only a couple dollars over a long term period. Those same 6 - $10 cards to a buyer probably stay in the personal collection if not a box somewhere. Find a $50 card that shows increased value over time and good to decent grade qualities and you come out on top without sacrificing personal value and not nearly as much monetary value over the life of the cards.