Anecdotally confirming. When shopping around for the past 10 years, I've usually bought used PCs and used parts, both desktops and laptops, but after deciding to try out a Mac in early 2012, buying used just didn't seem to be worth the discount.
It doesn't seem to be so bad right now, but part of this may be due to my insistence on getting at least 4GB of RAM for a MacBook Air, which was hard to find on the used market.
Adding to the anecdotes[1], of the last 5 computers that I have owned, 0/2 of the Macs are still running, compared to 2/3 of the non-macs. Because of this, I refuse to ever purchase a used mac, the discount is not worth the risk, especially considering the fact that it's nearly impossible to repair them on your own.
[1]Random idea for a website/service: Computer reliability statistics by model/year. Could be really useful for people in the market for used machines. Not sure how/where you would get the data though. Seems like forums are overrun with anecdotes, but actual data is few and far between.
Macs are quite variable in terms of good models and bad models. This seems to apply to both laptops and desktops. Unfortunately. I also haven't heard of a website or service that has the reliability statistics you want.
You didn't mention Applecare. It is transferable and is for 3 years. So if you buy a 1 y/o machine from a hipster who wants to upgrade, you would be covered for the remaining time.
It doesn't seem to be so bad right now, but part of this may be due to my insistence on getting at least 4GB of RAM for a MacBook Air, which was hard to find on the used market.