I just accidentally bought 50 base packs
fuck shit shit fuck fuck fuck fuck shit fuck shit fuck damn damn
Someone said somewhere they are allowing a one time take back or something. You're not the first to do this. But really, how hard is it to buy the right packs?
I did this also and here's my best explanation. (I only did it with like 14 packs and got a Grom out of one, which I was missing, so I didn't bother trying to get them switched.) There are a few things going on.
First: habit. If you buy packs often, the steps go: 1. Click shop. 2. Select quantity. 3. Buy.
Select pack type isn't a step in there, because previously there weren't any pack types. Habit is very powerful and subconscious, so it may well carry you through the buying process without you noticing that a new step is required. Habits are sticky, so even if you buy GvG packs correctly once, you may coast through purely on habit the next time and get the wrong kind.
But why wouldn't people pay conscious attention to pack type? That brings us to...
Second: misdirection. Picking quantity of packs to buy with gold involves arithmetic, which requires conscious processing. Even for buying packs with money, you still need to decide how many you want. It's only possible to consciously think about a single thing at once, so because you're thinking about quantity, you're NOT thinking about pack type.
Third: priming. A defense against habits is to notice that something "feels wrong" and direct your conscious attention to figure out why. But in this case, there were a couple things making the situation feel right. When you log in, you get a GvG banner, putting it in your mind. A lot of streamers also ran into trouble when returning to buy more packs after opening some already, which makes sense partly because they were already in a GvG mindset.
In conclusion, a lot of it comes down to performing the buying process subconsciously. Having the mistake be important actually doesn't matter that much as far as preventing it from happening. And as mistakes go, this one is fairly minor. If you want to read a vaguely related article, check out:
article (edit: warning: disturbing content).