Since I got a new 2017 Air from home insurance (spilled beer...) I wanted to know what my mid 13" 2012 Air is worth on the market (works perfectly except for 4 keys not working) and was stunned by the asking prices in Canada: from $600 to $700 on average! Really? For a 2012 13"? Looked at eBay Canada and prices are about the same.And about the same on eBay US also. So after 4 years the Air is still worth... 50%? I wouldn't have thought....
asking price != sale price.
Worth is always what a buyer is willing to pay for it. eBay is a good ref, but only the SOLD listings.
People ask wishful thinking prices. Personally I wouldn't pay $700 for a 2012 13".
For a tad more, you can buy Apple's refurbs from 2015 and be protected by 1 year warranties.
4 year old Airs to me should be around %35% not 50. 3 years is 50% for the higher spec'd version.
Lower specs, more inventory/market availability so price pressure downwards.
I keep seeing various iPhone 5S on a Canadian used website advertised for $375 and more, but market price is around $150-$200 ( I know coz we just picked one up as a backup phone).