In a recent interview with The Sun, Song revealed his motivation not to continue with the Gunners back in 2021.
Speaking to fellow Cameroonian Pascal Siakam of the Toronto Raptors, Song said, "When Barcelona offered me a contract, and I saw how much I would earn, I didn't think twice. I felt my wife and children should have comfortable lives once my career is over.
"I met Barca's sporting director, and he told me I would not get to play many games.
"But I didn't give a f*** - I knew that now I would become a millionaire.
"I'll always say that a 20-year-old who drives a Ferrari is a poor man, as at that age he's not yet achieved anything.
"But a man of 50 who drives a Bentley is a man to be respected."
In the interview Song also revealed that while he was at Gunners he was unable to save enough from his earnings.
He said, "Most footballers live beyond their means. I was at Arsenal for eight years but only began to earn a good living in the last four.
"That was because my salary went up a lot - but also because I came to realise what a waster I was.
"When I first joined them I was getting £15,000 a week. I was a young lad, and I was ecstatic.
"I wanted to rub shoulders with the big boys. I could shop wherever I wanted and have crazy nights out.
"I would go to training and see Thierry Henry - the King - turn up in an absolute gem of a car. I told myself I wanted the same car at all costs.
"I went to the dealership, signed the papers and arranged to pay for it by standing order - and just like that, I had the same car as The King.
"But I swear that I had to hand the car back inside two months. All my money was going on filling it with petrol.
"I told them: 'Give me a Toyota - this car's too much for me.'
"When I next went to training Thierry asked me: 'Where's your car, son?' I told him it's on a higher level than me.
"During my entire time at Arsenal, I couldn't even save £100,000, while people thought I must be a millionaire."
Song is now playing football in Djibouti with Arta Solar 7 at the age of 34.
At Barcelona, Song was able to do something he could not at Arsenal which is win trophies.
The Cameroon midfielder at Barcelona won the La Liga, Supercopa de España, and Copa del Rey titles.