What was the average age of the candidates? Might they be recent university graduates? 90% of recent graduates [around 2004 - 2010 give or take] are
absolutely bure kabisa!!! They are what I'd call the "mwakenya society". Students who rely entirely on copying - short notes, discussing, passing answers around, googling etc. - to pass exams. They use the 90 - 10 approach. 90% copying, 10% cramming. If you put such individuals in a situation where there is zero tolerance to copying and questions are primary application questions - as opposed to state, define, list etc. - then they are done.
A lady I know from UON once confessed she can't walk into an exam room without a "mwakenya" - even if she's not planning to use it! Same lady told me that some "big shots" in her class rarely sit for CATs or do assignments - they pay other students for the "service".
Never count on making a good sale. Have the purchase price be so attractive that even a mediocre sale gives good returns.