I bought 16GB of DDR4 in October 2014 for £213 for my X99 system when it was new and super pricey and then another 16GB for £65 in June 2016. Although the kits I bought has been phased out (HX424C12PB2K4/16) it appears the equivalent amount of RAM is costing almost just as much today.
Your first price is from 3 years ago.
Now, the cheapest 32GB 2x16GB kit that I can find is:
My basket at Overclockers UK:
- 1 x Team Group Vulcan T-Force 32GB (2x16GB) DDR4 PC4-19200C14 2400MHz Dual Channel Kit - Grey (TLGD432G2= £239.99
I think the problem with DDR4 pricing comes from the fact that for too long there is nothing superior, like DDR5 and manufacturers indeed tend to milk cows. Except that people can counter by simply ignoring purchasing and postponing to better times ahead.
Also, DDR4 has very wide spectrum of frequencies, it goes all the way from 2133 up to 4266+. Which is an insane range on its own.