Does any one know the cost of upgrading the memory on my iMac 21.5 2017 from 8 GB to 16 GB

If you have a mechanical hard drive – or a 1 TB Fusion Drive with a miserly 32 GB of SSD space – I'd suspect that the main reason for the slowness was starting up and running off that drive.

Other World Computing does sell RAM upgrade kits for 21.5" Retina and non-Retina iMacs.

https://eshop.macsales.com/shop/memory/imac-2017-21.5-inch

However, installing memory in those models is not an easy task. If you paid a repair shop to do it, the labor costs could easily cost more than the parts to upgrade to 16 GB or even 32 GB of RAM.

Unless the Memory Pressure graph in Activity Monitor is showing yellows and reds while you are running normal workloads, the extra RAM might not even do you all that much good.

The RAM is not the problem on your 2017 21.5" iMac. What is likely the problem is you have a base model with a glacially slow 5400 RPM HD. The only solution for that is to buy an external SSD and use that as your startup drive. Below is a link to instructions.

How to setup an external SSD as your startup disk

For your iMac I'd also suggest the following as the external SSD.

https://eshop.macsales.com/shop/owc-envoy-pro-sx

However, considering the advanced age (7 years old now) of your iMac you also may want to consider simply replacing it with a new Mac. All current Macs come with SSDs which are dramatically faster than what you own.

Hey there!

Often, this isn't due the amount of memory, but rather the storage your Mac uses. If your Mac is equipped with a mechanical 5400-rpm hard disk drive, you can use an external SSD as your startup disk which will substantially increase system performance for apps, startup, and more.

To see if you could benefit from this, check Disk Utility. In the Finder, choose Go > Utilities, then double-click the Disk Utility icon. (Disk Utility is located in the /Applications/Utilities folder.) Alternatively, click Launchpad in the Dock, type Disk Utility in the search field, then click the Disk Utility icon. Once Disk Utility is open, select View > Show All Devices in Disk Utility and look for the top-most drive. If that entry is labeled as "APPLE HDD..." or "Fusion Drive", you will see a speed increase from an external SSD.

To get started, I'd recommend reading this user tip: Use an external SSD as your startup disk … - Apple Community.

-Jack

Angler15 wrote:

Still such a nice computer. Only good for recycle at this point I guess.

There's a case for upgrading to a faster, newer Apple Silicon Mac … but also a case for simply getting an external SSD, making it your new startup drive, and upgrading to Ventura. As long as it doesn't suffer a breakdown, your Mac should have at least a couple of years of good use left in it (and possibly more).

• It has USB 3.0 ports – which are still current and useful.
• It has USB-C (Thunderbolt 3) ports – which are still current and useful.
• It can run Ventura. Ventura is one of the three most recent versions of the OS that get security updates from Apple and "love" from application vendors. It probably will continue to be for roughly another two years.
• If it has a Retina display, that's another point in its favor.

--------------------

To get macOS upgrades, see How to download and install macOS - Apple Support .

Note that if you are currently running a pre-Catalina version of macOS, and you upgrade to Catalina or beyond,

• 32-bit applications will stop working
• iTunes will go away, replaced by separate applications: What happened to iTunes? - Apple Support

Okay and best of luck.