Ever paid a restaurant bill only to discover they charged you for stuff you never had? What they did was bilk you — cheat you out of money that was justly yours. Shady companies are forever bilking their investors.
To bilk someone is slightly different from plain robbing them, though the effect is the same; it implies a non-violent, subtle and devious method masquerading as legitimate. Bernie Madoff, the Ponzi scheme king, was a classic bilker. On a more enjoyable note, one of the greatest bilkers in TV history was the appropriately named Sergeant Bilko, played by the comedian Phil Silvers. His eternal card games, promotions and get-rich-quick schemes were all designed to part some poor sucker from their cash. Watch and learn from the master.