Before budget airlines, I used to fly on courier tickets. Available from Golden Mile then. About S$150 to and fro Bangkok, S$500 to and fro Tokyo (Narita) and S$800 to and fro US (SF or LA). Those days the S$ rates were very much lower and those fares were very cheap at abou 50% discount to market. The courier ticket had the restriction of no check-in luggage. They'd use your check-in allowance for whatever they wanted to send. There's no worry about drugs or contrabands. It was legal company and legal separation of passenger seat from luggage allowance.