Joseph – let’s break it down further
1. “At that point the original $100 is no longer considered to have been given to maaser, since you got it back, so you’d have to give that $100 to maaser (since it presumably came out of your maaser cheshbon.”
——how do you go back and readjust where the money came from? It’s not a game. Secondly, Winning a chance prize is not as if you got your original money back.
2. Has just negated your original theory of having to reduce any amount of the winnings or investment from your Maaser Cheshbon even though you have proven to have gained from it personally.
The idea is, we have to establish who’s money won the prize? Your own… then deduct it from the original ticket price and keep the prize or it’s Maaser money investment and Maaser gets to keep the winnings. In that case all $3000 should belong to Tzedakah as you have donated all the money to it.