Apple
It's called the Refurbished Mac store, and you can find older products that are less expensive than the newer products you'd find in Apple's main online and physical outlets.
Some of the products are certainly too old to consider buying, no matter how tempting the price tag, and others simply aren't good deals. But there are some more recent products that will suit most people just fine.
As you may have guessed, the Refurbished Mac store sells previously-owned devices. I can understand if that idea puts you off, but if the $4 is anything to go by, Apple's refurbishment process is excellent. My refurbished MacBook Pro is in perfect working order, and it looks brand-spanking new, too. I saved $450 by going with the older refurbished model.
Refurbished device quantities are limited, so you may not find the exact model you're looking for.
Check out the best Apple devices to get from the Refurbished Mac store: