SpaceCadetGemmellnesspeople spend loads trying to unbox a knife. vids on youtube of knife unboxings are pretty much the same as le epic jackpot win!!! vids.
I think you answered your own question. If someone is spending money to buy something, then it is not gambling.
Buying keys means you are purchasing whatever items you unbox. That is a clear difference than gambling your items for money or other items.
Stop with the Valve fanboyism please. The crate opening system, especially in CSGO is as much gambling as using tokens in casino is gambling. Just because you are not directly using money and instead using an intermediary system (skins/casino tokens) does not change that crate opening is by definition gambling.
Using keys, which have monetary value, to open crates, whose content also has monetary value, with a small chance of turning the initial investment to profit, is per definition, gambling. The crates work pretty much exactly as slot machines do, and this way of gambling poses the same threath to children's mental health as conventional gambling does.
I'm not even saying that gambling is inherently bad or anything, in fact gambling is fun to do and should be allowed for adults, but Valve is definitely promoting gambling to their audience with their crate opening system, and this audience has a lot of kids in it. It's pretty much a legal loophole which allows kids to gamble because Valve claims that skins do not have an inherent value, even though this statement is blatantly wrong.