The only Psychedelic Rock I can think of that early Sabbath sounds at all like is Blue Cheer and maybe a bit of Iron Butterfly and Steppenwolf. And by the time of Master of Reality they were pretty far removed from that; this is colossally heavy, chugging music that sounds far more similar to the Doom/Sludge Metal of the mid- to late-80s and early-90s than it does anything previous or contemporary. Not only is this an incredibly influential Metal record but it also sounds much more recent than 44 years old.
No one else had anything approaching Tony Iommi's guitar tone in 1971. Anyone who is into doom/sludge/stoner metal (I'm a big fan of that stuff) needs this album and should worship this album because it pretty much singlehandedly spawned those genres. If you play this for some unsuspecting soul in 2014 they would never guess from the guitar tone alone that it comes from all the way back in 1971. I can't stress how incredible it is that Iommi got this kind of heaviness from his guitar and amp way back then.