Oh yeah, in 1986 Reagan administration introduced tariffs for 64K DRAMs from Japan. I remember having a bunch of trouble tracking the chips down so I could upgrade a 128K Macintosh to a 512K "Fat Mac" (which was easy to do, if you had one of the oddball new Torx bits -- also hard to find -- and a soldering iron stalwart enough to defeat the massive and heatsink-like ground plane on the Mac motherboard).
512K for about $240, IIRC. My first major purchase at Fry's, which had recently bifurcated a supermarket into a "chips" side (with dip) and a "chips" side (with sockets).
As for the XE, from reading the forums it sounds like they just used a bad batch of 4164 DRAMs, something to do with them being American made and not Japanese. I seem to remember this was the era of crazy fluctations in memory prices.