Johnny Manziel is still living VERY large -- despite the fact he hasn't had an NFL paycheck in a very long time.

The embattled QB pulled up Wednesday to Barneys in Beverly Hills -- one of the most expensive stores in town -- in the driver's seat of a custom Rolls-Royce.

Later that night, he hit up Warwick in a Givenchy sweatshirt, which retails for more than $1,000.

He's also planning a wedding, renting expensive places to live and traveling. So, the question is ... how can he still afford to live so lavishly?

The answer? Manziel is said to have raked in about $7.8 mil from his rookie deal with the Cleveland Browns -- plus, he made a ton of cash from endorsement deals with companies like Nike and Snickers.

Plus, the family reportedly has oil money -- though it's unclear if Manziel has access to it.