Some interesting comments...
I had a LC a couple years ago. It was a '94. Sold it and bought a '97 LX450. I wasn't looking for a Lexus, per se, but found one with lockers and went for it.
THE LX 450 IS THE SAME AS THE LAND CRUISER.
With some minor exceptions...
1) body panels -- this is obvious...LX has them, LC doesn't. This means that the quarter panels and the doors are not necessarily interchangeable -- unless you want to drill the LC doors/quarter panels to fit the LX plastic body panels...uh...that should be body armor not body panels.

2) corner bumper pieces on the LX are fatter than the ones on the LC. This is only a problem if you get an aftermarket rear bumper (like slee's). The mud flaps will not fit flush -- so if this is a problem...you get toyota mud flaps or run without them.
3) grill and head lights are different. Headlights are not interchangeable between the two. But I suppose if you swap the grills and the headlights, you'd be okay.
4) stereo is different. LX comes with 6CD changer under the center console and no in-deck cd player. And it sounds a hell of a lot better than the LC set up...but not neccesarily as good as some aftermarket stereos/speakers.
The rest of the differences are either cosmetic or not worth mentioning. I've also heard that some Toyota dealerships will not guarantee work on Lexues. Seems real stupid to me since THEY'RE THE SAME VEHICLE (with those few minor exceptions I mentioned).
The reason I bought the Lexus is that it happened to be a better deal than any Toyotas I found at the time. And it was certified pre-owned from Lex, so I got the warranty got extended to 100k miles and it covers everything except the clock and chromed parts ??? (9k miles left before I'm on my own for most repairs

). They've already fixed a bunch of stuff for me at $0 charge to me.
As for why the LXs are less expensive? Don't know. Probably has to do with where you live and how many are out there. As I recall, you're in the general south bay area of CA -- I'd say that you're running across a bunch of ex-silicon valley dot-com soccer mom rigs and the soc-moms are moving up to LX 470s.
It's true that Lexus parts are more expensive...if you buy them at Lexus. I buy my parts from my favorite Toyota parts guy. The only Lexus parts I've gotten have been thru the warranty. Funny thing...all these "Lexus" parts came in TOYOTA packages.
My $0.02...get the best rig you can find for the best price (one with lockers, of course).
LC vs. LX shouldn't make a difference.
So -- you gonna keep the '91 too?