Well I have all three at home right now (RS-1/HP-1/PS-1). I would say that overall the HP-1 is the superior phone. This is a preferences thing. Though I'm not alone here at least.
PS-1 bass is bumped quite a bit, it is tighter than the RS-1 but only marginally and I attribute this to the metal vs. the wood. The sound is unbelievably smooth and liquid. Best sound in this regard I have ever heard. Beagle believes this is due to the destressing of the driver as compared with the RS-1 that only has say..two coats or whatever. I would agree with him.
The weight is substantial with the PS-1's but I don't mind this at all. I actually like it, as I do like the HP-1's (though they are lighter). RS-1's however are a pleasure to dawn after having those heavy brutes on for an extended period of time.
As for the highs, the PS-1's take care of the sheen or hint of brightness from the RS-1's as well as attenuate or better yet, eradicate the Sss sound that can be heard with RS-1's. For these reasons alone I would buy the PS-1's.
What I like about the RS-1's: tone and body for woodwinds and strings. For me, no other headphone matches them in this regard. The R10's coming close but falling short because of that odd fake sound due to their closed design. (for me at least). I also like their price. Used - about $400 USD. Not bad at all.
What I like about the PS-1's: liquid sound, wonderful highs. Bass is too strong with most recordings when using my premium tubes but if I swap them for a thinner european tube this attenuates the bass and they are truly magical. For those with SS amps and no possibilty of a lot of rolling of opamps (I find them to be less effective at tone controls than tube rolling anyway) then you may find them to have too much in the bass.
I find they both have the same level of detail though with the more bloated bass of the RS-1's (in comparison, one would hardly call it bloated in comparison with other cans...) the detail can be obscured (as I have commented on when comparing between HP-1's and RS-1's and now too with the PS-1's and RS-1's.)
Are they worth double the retail? Not for me personally...not when I already own the RS-1's and HP-1's. I find the HP-1's to be my prefered sound all around (Better bass control and tone, flatter sound, more transparent) but that is just me. I enjoy lots of PRaT. All Grados have this in spades. I also enjoy a palpable sound, a lot of *snap* to my notes. HP-1's do this better than any phone I have heard to date, save for perhaps the Ety's (though very fast and with a palpable sound, it simply fails to match the equivalent in the open designed phone).
My third most desired outcome is wonderful tonal balance for strings and woodwinds, this is my main reason for keeping the RS-1's around. They just do it better to my ears.
Anyhow, to each his own I suppose. Some will be fortunate enough to own all three.