This is another one that falls into the "spend money to save money" category. Believe it or not, there are quite often coupons slipped into the envelope your bills arrive in (assuming you still get them through snail mail).
There are coupons that fit at least somewhat within the category of the bill. Your car insurance bill may have a coupon offering a discount on life insurance for a limited time. A power bill may come with a savings voucher you can activate if you buy certain energy-efficient appliances.
And then there are the coupons for somewhat random goods, and these often accompany your credit card bill. You'll find discounts on things like class rings, fine jewelry, stationary and engraving services. Self-serving cross-promotion at its best. And hey, if you're already in the market for a class ring, you're golden.
And finally, the moral of the coupon story ...