Not crazy at all. I'm a sucker for freebies too. I bought a pair of shoes at DSW a few weeks ago just because I liked the free bag they were giving away with purchases. The shoes are okay but I love the bag.
You're not crazy at all! At least you'd be buying something you'd use everyday (lotion, soap etc) and the bag looks pretty functional too. It'd be different if you were talking about buying something you'd never want/use/need OR if it were more than $20. Go for it!