Surely, you might have considered buying whatever is the cheapest Splinterlands card at the time, but you'd quickly think you're better off buying a variety of cards instead of the same one every time. Because it's obviously a stupid idea... Right? Turns out it is an acceptable strategy. Even if you exceed your target amount of BCX for a single card, it's never going to be useless.
Collection power. You can sometimes have too much power. If you're only 20k power above your league, but you still need 30k for the next division, renting excess power is acceptable. When that happens, what are you going to rent? Anything you haven't been using frequently. Which can include a bunch of the same card. So excess is still useful.
If you're rushing collection power, buying something you don't need in matches is okay, specially if you're already winning more than 50% of your ranked battles. It provides the power you need, it's always easy to sell it off on the market if you need the money back, you can rent it out, and its price will eventually rise when it goes out of print - so it's never a lost cause.
