It cost A LOT of money for Tom Brady to look so dressed down at Fenway Park on Monday -- his casual stadium outfit cost almost $2,000!!!!

Tom was mostly decked out in Tom Ford -- with a merino crewneck sweater ($790), some fit black jeans ($680) and a $380 pair of sunglasses.

Throw in the Under Armour shoes ($85) and you're right under $2k.

And that doesn't include the $10,000 TAG Heuer watch on his wrist -- or the $500,000 Super Bowl jersey in his hand!

You fancy, huh?!