Well.. this story directly provides an answer (potentially) -they get an additional marginal ranking benefit inside some market appraisal score because they double their international successful completion count, for low marginal cost of posting negligible weight content to you successfully. The benefit to them is fraud, but not against you: its against the ranking engine inside some digital marketplace like alibaba. You are an unrelated third party who validates (by accepting) delivery. Since you don't know if the package is shrinkwrap "free gift" or the $20 meter, you accept. Are you willing to monty-hall reject the random package :-)