You have to keep in mind that just because there are some impurities, it is automatically dangerous. Compare the risk of not having an epi pen available when needed to the cost of keeping one stocked if you are not particularily high-risk, and you see that it doesn't make sense for the unnecessarily expensive ones. If they were cheap enough I'd keep some stocked to have handy when handlign potentially allergenic substances, just in case I happen to actually be allergic. But this <5% chance of having an allergic reaction of significance, and then figuring that only a small part is life-threatening, as well as the cost of one's live, and setting this agains the cost of keeping stock (it goes bad), it doesn't work out....