Game-used and signed HR ball

[nationals2k9]

I am just looking for any opinions on the rarity and potential value of an actual HR ball hit during a game that has been signed and dated by the player. I would like to think this is a pretty rare feat all things considered since 1) getting a HR ball is very tough and 2) having the player tracked down to sign and date it accordingly isn't easy either.

Granted it depends on the caliber of the player (in this case pretty good)... but just wanted to see what some collectors know about balls like this and how much they have sold for in the past.

Thanks!