Brady's Backup Jimmy Garoppolo -- Now Worth Almost as Much as Tom!! In Trading Card World

If you're in the market for a Jimmy Garoppolo card, you shoulda bought it last week -- 'cause the Tom Brady backup's trading card is SKYROCKETING!

Ever since Brady was suspended ... Garoppolo's been a hot commodity, and not just for Bill Belichick. TMZ Sports found out his signed rookie card is worth more than 100 times what it was before Tom got nailed.

A rep for COMC -- a top online auction site -- tells us ... "His card was originally selling for $2.25, but as soon as Tom Brady's suspension was announced, Garoppolo's card skyrocketed to $278."

Put down your smartphone ... we already did the math, and that's a 12,256% increase. By comparison, the rep says a signed Brady card will set you back about $290.

Trading cards are nice and all, but Tom still has the 4 Super Bowl rings ... and Gisele.