If it were to become illegal no one would buy it as Razor would would no longer make it. Razor is a respectable company, they're not going to produce an illegal product in case they get caught, and no one else has the recipe so no one else could make it.
The cost is only $40 US for three doses, and 3 doses is about 15 days assuming you use it constantly. So that's $40 for 2 weeks, not really that expensive.