Managers...Good or Bad.

what ive come to when it comes to managers is twisted. i can talk to a major artist, get his ok on purchasing a beat but then the manager turns around when he/she breaks wind of the deal and theyll shut it down if it isnt proposed correctly to them or if they feel left out(meaning no cut). Like a major artist im in the process of getting a feature from. The artist and i have a pretty good relationship and he is perfecto wit trading one of my beats for his verse(feature). Now the manager is hitting me up saying make a decent CASH offer. No offense but we already had this planned and maybe the managers right cause they deserve there cut, but if they didnt get the business why do they deserve the financials from it? whats your thoughts? and experiences?