It's all about context folks. If the batter was po' boy that just loved to play the game and that was all there was to it, then I'd give it back. But that just ain't the case. Just to BE in a position to catch a ball at a game costs silly amounts of money...that goes to the owners and their employees/contractors. This particular batter doesn't bat for free. He has an agent and they negotiate his pay as high as possible before the player provides his services. That, in turn, raises all associated costs to the fans. Now this is all just business, and that's fine. But when the ball lands in your lap and the shoe is on the other foot, don't go saying "It's right to give it back.".
By the leagues own example, when you have something of value you KEEP IT until you negotiate an exchange for the highest possible monetary value.
If they want the ball back, they can remove profit from the game. Until then, there is NOTHING wrong with being just a capitalistic as the game that charged you for your seat.
Like others have said, $250K would make a REAL difference in the lives of most folks and it's a mere drop in the bucket for a premiere professional athlete.
It's good to be nice, but being nice doesn't mean you can't make a profit as a participant in the business.