$1,000 could be a DEAL when it comes to getting Tom Brady's autograph ... so says NFL Hall of Famer Shannon Sharpe, who tells TMZ Sports the G.O.A.T. could charge A LOT more.
TMZ Sports broke the story ... Brady is doing a private autograph session with a sports memorabilia company next month and the prices start at $850 for a photo! Footballs are $1,000.
But the co-host of FS1's "Undisputed" says Brady could charge more than DOUBLE that if he wanted to ... because it's not about what you ask ... it's about what people are willing to pay.
He also left us with this gem -- "There's nothing free in life but salvation and televangelists charge for that ... so there's nothing free!"