Buying guide · prices checked on 14 November 2026

A used 5K iMac as a monitor: what it costs and which one to buy

You don’t have to own the iMac already. A refurbished 27-inch 5K iMac costs less than any new 5K monitor, and with one cable it becomes the display for a Mac with Apple silicon. I make SecondGlow, the app that does it, so check my sums: every price links to where I found it.

The sum

	Price	Where
27-inch 5K iMac, 2017, refurbished	from $257	Mac of All Trades
SecondGlow	$39 once, after 7 days free	Pricing
Together	about $300, plus a USB 3 cable if you don’t have one
Cheapest new 27-inch 5K monitor I found	$509.99	KTC H27P3
Another budget 5K monitor	$699	Kuycon G27XSE
Apple Studio Display	from $1,599	Apple

US prices on 14 November 2026. “From” is the dealer’s lowest price for the base model. Private sales can be cheaper; I haven’t tracked them.

Which iMac to buy

Model	Refurbished, from	Verdict
27-inch 5K, 2017	$257	The one to buy. Half the price of the cheapest new 5K monitor. USB-C ports, so a Thunderbolt or USB4 cable works too
27-inch 5K, late 2015	$199	The cheapest that works. USB-A cable only. It runs macOS Monterey, the oldest macOS SecondGlow supports
27-inch 5K, 2019	$384	Fine if you find one near the 2017 price. At this price a new 5K monitor is only about $90 more
27-inch 5K, 2020	$577	Don’t buy it for this. A new 5K monitor costs less
21.5-inch Retina 4K, late 2015, 2017, 2019	$179 to $272	For a small desk: 4096 × 2304
27-inch 5K, late 2014 and mid 2015		Won’t work. Their last macOS is Big Sur

In Germany, classified ads ask a median of about €385 for a 2017 model and about €500 for a 2019. Those are asking prices, not what the iMacs sold for.

Buy the cheapest configuration. As a monitor the iMac only shows the picture, so the processor, memory and drive hardly matter. My own test iMac is a base 2019 21.5-inch with an i3.

Check before you pay

The year, exactly. “2015” isn’t enough: the mid 2015 5K iMac stops at Big Sur and won’t work, the late 2015 one runs Monterey and will. Ask for the model name from About This Mac, or the model identifier: iMac17,1 is the late 2015 5K, iMac15,1 is the one to avoid.
The screen. Ask for a photo of it showing a plain white page and a plain grey one. You’re buying it for the panel.
macOS Monterey or later installed, or the seller’s word that it can be.
A keyboard and mouse for the first ten minutes. You need them once, to install SecondGlow and turn on automatic login. After that the iMac starts as a display by itself.
The return period. SecondGlow is free for 7 days, so you can test the whole setup on your desk while the iMac can still go back.

What a new monitor does better

It works with everything. A PC, a console, an Intel Mac. An iMac with SecondGlow is a display for Apple silicon Macs only.
It uses less power. Apple lists 63 to 74 W idle for the 27-inch 5K iMacs it tested. A Studio Display is listed at about 32 W switched on. The two were measured in different ways, so take it as a rough guide.
It’s only a display. The iMac is a computer that has to be on and logged in, and it gets no more macOS updates.
Charging and ports. Many new monitors charge a laptop over the same cable. The iMac doesn’t, and its camera and microphones aren’t used.
A warranty, and no second-hand surprises.
Games. For competitive games a direct display cable is better.

What the iMac does better

Price. About $300 all in, against $510 and up.
The panel. 5120 × 2880 at 500 nits with wide colour (P3) on the 2017 model, in Apple’s aluminium case.
Speakers. Your Mac’s sound plays through the iMac.
A spare Mac. Unplug the cable and it’s a computer again.

So, is it worth it?

Yes, if you have an Apple silicon Mac, work at one desk, want Retina sharpness for the least money, and don’t mind a second computer humming along as your screen. Buy a 2017.
Buy a new budget 5K monitor if you want it to work with any computer, or would rather pay $200 more for a warranty and nothing to set up.
Buy a Studio Display if you want the camera, the microphones and one-cable charging. SecondGlow vs a new Studio Display.
Already have a Retina iMac? Then it costs you $39. Every way to use a 5K iMac as a monitor.

Try SecondGlow free Check compatibility

Sources

Prices checked on 14 November 2026. They change; follow the links for today’s.