LeBron James Dropped $5k On Halloween Costume

LeBron James has proven yet again that he's serious about his Halloween costumes ... he dropped $5k to make sure his "Martin" inspired look was LEGIT for the Cavs' party ... TMZ Sports has learned.

LBJ hit up Teheran Jones from Exclusive Game in ATL -- who works with big names like Cam Newton and Rick Ross -- to make the Jerome outfit from scratch ... using real MCM bags to make the costume.

All the work paid off ... 'cause Jones says Martin Lawrence personally hit up LeBron just to tell him how he loved the look.

We're told it was a quick turnaround and Jones had one day to complete the order ... and LeBron had to fly his assistant to Atlanta just to pick it up.

#ItsGoodToBeRich