Buy 4 bottles of Windex @ $3.98
Use two $1 printable coupons
Use two $.55 peelies (It's up to the store as to whether or not they'll allow this)
Pay only $1.98 (or $0.88) for 4 bottles
You can also submit receipt for the $5 SC Johnson rebate (limit of 3 rebates per household). Even without the rebate, your cost per bottle ranges from $0.22-$0.40. Add the rebate and you've got a nice little money maker on something almost everyone uses. Much like the free Scrubbing Bubbles deal last week, odds are this won't last long so don't wait!