AT&T's offer is $29.99 with a new two-year service agreement. The normal price for a 16GB Samsung Galaxy S4 is $199.99 (again, on contract).
To be clear, AT&T calls the refurbished devices "like new." Frequently, a refurbished device isn't even one that has been returned for defects. Some such devices were simply returned because the end user decided the device "just wasn't for them."
In those cases, the device is basically, yes, like new. It is possible that the device will have had to be repaired in some way or another, or that it would have minor cosmetic defects.
AT&T describes these refurbished devices as follows:
AT&T Certified Like-New Device
An independently tested and reconditioned pre-owned phone with at least a 90-day warranty. Good as new and good for the environment.
This year, Samsung switched from Roman numerals as the flagship device, expected to be dubbed the Galaxy S IV, became the Galaxy S4. Last year's model was the Galaxy S III; the prior year's was the Galaxy S II.
In the U.S., the device sports a quad-core Qualcomm Snapdragon 600 processor running at 1.9GHz. In some parts of the world, meaning those sans LTE, the device ships with a Exynos 5 Octa eight-core (more or less) process. That processor uses ARM's BIG.little architecture, but does not have the capability of running all eight cores at once.
The device currently runs Android 4.2.2, but is expected to get an upgrade to Android 4.3 in October.
It has a 5-inch screen, up from last year's 4.8-inches, and has dimensions (in inches) of 5.38 x 2.75 x 0.31. The Samsung Galaxy S4 weighs 4.59 ounces.
The screen is a 1920 x 1080 HD Super AMOLED display. That resolution at that size gives the device a 441 ppi measurement, putting it far above the definition of a Retina display, which Apple says is 326 ppi -- or at least, its current and past iPhone models with Retina displays sport that measurement.
Those wondering about battery life can be reassured by the fact that the device carries a large -- and user-replaceable -- 2600mAh battery.
It also received some nice camera upgrades over 2012, with a 13MP rear-facing (4x digital zoom), including live video capture and playback 1080p with dual camera mode (meaning front-facing and rear-facing) and slow motion video capture.
The front-facing camera sports 2MP resolution.
AT&T says the deal is a limited time deal, but does not say how long it will last. Typically, these sorts of things run only until supply is exhausted.