In the space-invaders film "Signs", former Episcopal priest Graham Hess has a hard time wrapping his head around the idea of yelling profanity while trying to rid his property of prowlers, since he was not accusstomed to speaking that way.
Being tricked into buying something you think will reap hugh benefits down the road when in reality it's not worth shit. A long con.
Dave bought into a company cause he thought it had great potential but he got fucked over, and the potential was greatly exaggerated, ultimately he realised he'd been "accustemmed"