I always thought they did, but it seems to depend.
I've just researched this now. I bought my 7 Plus 128GB in 2016 for 96,000 Yen (I'm in Japan). The Apple Store is still selling the 7 Plus 128 GB in 2019, for 75,800 plus tax at 8%, so roughly 81,000 Yen. Considering it's 3 year old tech, the price hasn't dropped that much...
In one way, it's quite a compliment that I 'chose wisely' with the 7 Plus as it's still good enough to be sold new in Apple Stores, but on the other hand, it's a shame. If they dropped the price to half or less, I'd get a new one of those when mine dies instead of getting into the $1,000 plus model rat race...