I keep a spreadsheet like this as well to track my Platinum, Delta Reserve, and Bonvoy AMEX statement credits, but I usually just put $0 if it's something I went out of my way to purchase just b/c of a statement credit. I put $0 whenever I access a lounge as well, even though I usually would spend money elsewhere in the airport if I don't have lounge access. I guess I'm a huge nerd because I like tracking this stuff and seeing what value I can get out of the cards.