There probably should be some sort of requirement where the H1-B visa holder's peers are required to anonymously rate the abilities of the H1-B visa holder relative to themselves after something like 6 months of employment. This wouldn't prevent the hiring of workers at a lower rate but would provide a quick enough correction to such fraud. It would also make sure that H1-B visa holders are paid a fair wage relative to the value they bring.

Prior to getting an H1-B employee the employer would be required to register a minimum number of employees that will be a peer of the new employee (no bosses or anyone else that may be in cahoots). After 6 months, the government agency responsible for such visas would send a survey to those peers asking them for their title and salary and stating the title and salary of the H1-B employee. They are then asked to rank the title and salary of the employee against their own as well as the skills of the employee relative to their own.