And I think the problem s/he (and I) have here is that it is not up to each individual to decide whether to declare purchases over the legal limit, just like it's not up to each individual to lie on their tax return. If they do that, they are breaking the law and, while there can and should be legal consequences, it is also a "wrong" thing to do.
Sprite
As with any rule or law, the hope is that it won't be broken but we cannot force people to obey and so everyone chooses to comply or not. So it is up to each individual to make their own decisions about what they do. I'm not saying that's right but it's how it is.