If you are buying a 2014 model, given that it seems to be non-upgradeable, I suppose the answer is "yes if you want that much memory." Whether you want that much memory depends strongly on your application needs.

If you already have a 2012 mini or earlier, I would look at crucial.com. It looks like the 2012 models are pretty easy to upgrade. Older models, I know from personal experience, are quite fiddly and difficult to take apart, so I wouldn't recommend it unless you have experience taking apart laptops and tools available such as spudgers and spatulas and extra kapton tape.

FWIW, i used a mid-2011 2.3Ghz i5 with 8 GB of RAM for about 4 years as a lightly used dev machine (read: basically ruby/rails, pg, and sublime text with some crud stripped out and running on OS X [not server]) that also hosted about 25-30 (low bandwidth) rails apps for internal use that did a lot of text processing and never really had too many complaints. flash forward 2 years of sitting idling without any activity and it's a bit sluggish now (granted that's because i've done literally nothing on the machine other than let it run)

What is it being used for?