In my experience, opening booster packs from Splinterlands is not so reliant on luck. Market prices are quite accurate most of the time, unless it's something that just released. So if you buy a bunch of packs, you'll seldomly lose more than 10%. Whatever I get usually evens out - which happened to be the case with my 102 chaos legion packs.
I got very unlucky with gold foils. No summoner gold foils, yet again no legendary gold foils, but that's kind of taken for granted I guess, and generally lots of regular common cards. More than I usually get. STILL! I got pretty much the exact value I invested. Yes, let me explain.
As soon as I was done opening (using double potions, of course), peakmonsters told me the total value of my cards. Considering I'm selling them for 1% less than market prices and that I'm losing 5% as market fees... It came down to the exact same USD value I paid for! Down to the dollar! Haha.
I didn't sell all of them, though, but most are gone. Right now, I'm delegating a few cards to a friend who's playing and splitting the money with me. He has pretty much nothing except my cards, but he's having fun, because Splinterlands is a fun game. After telling him about Axie and Splinterlands, I suggested he'd have more fun with Splinterlands, which he agreed. He's been playing for over a month, craving for more.
In the image at the beginning of this post, you can see the cards I've delegated to him. Oh, I'm sure you thought for a moment those were the entirety of my booster pack drops, but nope. Posts look better with an image at the beginning, you know!