Hi ppint, I think a large part of the US angst over the price of those two Atlantic best-ofs was because of the age of the tracks, and so it was felt that, because they would have recouped their costs many years before, there was less justification for a full price, whereas the examples you cite would only have been within a couple of years of recording.
philmh: strange; yr hmbl srppnt. didn't expect to buy greatest hits/best of lps more cheaply than the standard "full price", whatever that happened to be - 22/6, 23/6, 25/-, 27/6, 29/11, 32/6, 35/-, 37/6... - at the time. but did feel the jimi hendrix experience "smash hits" lp was rather a rip-off, and was disgusted at/by greatest hits/best ofs that palmed off re-recordings° that were audibly not the same as the hit (or non-charting) singles - which was very often the case with the stereo best ofs/greatest hits lps. "live" lps always struck me as a rip-off, though - or almost always: poorer performances, poorer sound, fewer tracks... - but there were some exceptions, later on - especially memorably, two or three of the allman brothers band's albums, almost all of which i realised'd been taped live at the same concert, and yr hmbl srppnt. "restored" into one long recording on a reel-to-reel tape.
° - the young me didn't know of any reason why music & record companies should, or even might have needed to, do this and, after getting burned by this a couple of times°°, carefully stuck to mono for a long time - years and years, even
°° - the stereo lps never warned that these were not the original recordings
Probably cut down for publishing reasons; I think US publishing royalties around then were ten cents per track (as against the UK and elsewhere publishing regime of 6.75% of the price of an album), so the more tracks you have on an album, then that's more that has to come out of the revenue, so it was (and is) common in the USA to drop tracks if the album is sol at a lower price point. For the same reason, greatest hits compilations can often retail for full price, even if the tracks are 10-20 years old or more. I remember in the 1990s a big to-do about Atlantic selling new best-of compilations by Roberta Flack and Bette Midler at full whack; Ms. Midler apparently complained loudly about this, with the result being that Atlantic cut the track list for the US version of the CD (EXPERIENCE THE DIVINE) from 18 tracks to 12, whereas the international versions had the full track list.