No, it doesn't have to be a Samsung card in a Samsung device. I've used several big brands, and ironically the only one I've had problems with was a Samsung card used in a Samsung device! But any manufacturer can produce a dud, so a single data point like that doesn't mean anything (and I really mean that it is of no significance). In fact very few people will use enough cards that their experience by itself will be statistically significant.
I don't know what price to expect because I don't know where you are. But usually if you look at prices on Amazon (for cards sold by themselves, not by a marketplace seller) or a big name vendor you'll get a fair idea of the going rate. Be very wary of anyone who seems to be dramatically cheaper than that, and under no circumstances buy from eBay or some random Chinese online market: there are a lot of "fake" cards out there, and the old rule "if it seems too good to be true it probably is" applies very strongly when buying SD cards.