Are some MTG sets statistically more likely to yield more valuable cards?
You're thinking about this as if you are buying packs to sell the cards, but are you really buying packs to play with the cards?  Unless you are likely to immediately sell the rare cards out of your pack, picking ones based on the current selling price is pretty much meaningless.  If you're buying to play with the cards, it would make a lot more sense to think about cards that you are interested in adding to your play collection, and then buy the set that gives you the best chance of getting those cards.