This "loophole" is likely to be motivated be the cost of processing small transactions. If customs officers spend two minutes per parcel, then it makes sense t

This "loophole" is likely to be motivated be the cost of processing small transactions. If customs officers spend two minutes per parcel, then it makes sense to exempt parcels for which the expected revenue doesn't even cover one minute's labour cost. Where I live, parcels with an expected revenue below the price of a cup of espresso are exempt. The definition is different, of course.