"I'm not in this for the money because if I was, I would have jumped out after our first album"

Justin Timberlake is expressing that he is not inspired by cash. He remains in the music industry for the love of music and not for the financial gain. He is suggesting that if he was just in it for the money, he would have left after the success of their very first album. This recommends that he remains in it for the long run and is not simply searching for a fast monetary gain. He is enthusiastic about music and wishes to continue to make music for the rest of his life. He is not encouraged by money, however by the delight of developing music and carrying out for his fans. He is in it for the love of music and not for the money.