What sustains human trafficking?

Quite simply it is the failure of all Governments to ensure Global Databases which can be used to trace track and locate activity related to human trafficking are on a common platform in every Country of the World.
The Database set would include financial transaction, shipping movement and known persons and their community relationships. Human Trafficking has to be financed and the numbers are not small. The funds must cross borders and at some point must be removed from its 'ghost system' into the 'real system'.

Our Governments are weak, soft and unwilling to confront a growing problem. Until we have principled 'tough on crime Governments' women and children continue to suffer and when they are of no further use they will be murdered and in some cases their body parts will be sold. A lot of people make money out of the pain and misery of the women and children and men too who are trafficked. We need a Global Platform to collect information and tough Governments to use the information to arrest those concerned. Unfortunately we have neither.
Money sustains human trafficking. Like all illegal industries that survive, the profit overcomes any losses or deficits incurred as a result of the process being illegal.

As concerns the specifics of how profit from human trafficking sustains the industry, this depends on the type of human trafficking. In the case of trafficking women, the "investment" in moving the woman is more than covered by the fees that will be paid to her traffickers for sex with her for several years. In the case of slaves, the cost of trafficking is paid when the slave is purchased by the "End User."