Rockstar said why they cut the Mission Payout were reduced by 50%.
"This is to keep the game balanced as well as encourage the exploration of new missions and content in the game."
"We understand players do like to enjoy a mission multiple times, so rather than remove the possibility of doing so, we've allowed replays of these missions at a reduced payout. Many players can get very good at a mission and beat it much faster in consecutive tries, so we've adjusted these payouts to match that case.
"We apologize that there was not full clarity about this in the patch notes; however, hopefully this note will clear things up. If there are any additional questions, please do not hesitate to ask."
"Considering Rockstar recently announced all GTA Online players will be receiving $500,000 in-game to apologize for multiple launch issues, it's possible this is a move to stop everyone getting too much too soon."