I think there are differences in the law between importing and exporting perscription drugs - importing having tighter regulations than exporting. Since the prices are in US dollars, I'd say this site is exporting to other countries, at which point the legal onus is on the importer using another countries laws. Just a guess though. But I highly doubt you'd be able to legally buy them yourself. This company is proabably relying on the loopholes to keep themselves out of trouble, but that doesn't mean the purchaser isn't breaking the law.
I'll try to find the source of where I read about the differences in the import/export laws. I'm sure it's around here somewhere. Until then, assume that what I have posted is just heresay.