alt Hacker News> If you intend to purchase an item from the merchant anyway, why would you pass on 20% off?
Most discounts I run into seem to be based on incredibly inflated pricess to begin with. If a shop offers me a 20% discount on something it is often cheaper to buy it somewhere else.
When I subscribe to these I've usually already found that either they are the only shop to carry that product, or are already the cheapest. The 10% discount is just an extra at that point.