I recall reading stuff about his attitude being not great and also his preparedness to contribute next to no goals but keep banking the pay cheque (could have moved on with a pay cut and tried again somewhere else). But - based on your challenge - I've done some reading and what I've found...
He'll sit there taking his £120k a week until the contract runs down and ends at the end of next season (https://www.spotrac.com/epl/crystal-palace/christian-benteke-15494/). £8m isn't cut price, it just reflects a player with one year left on his contract (free to speak to other teams in Jan)...