I wouldn't drive a 200SX if any of the other cars above were available - even if the 200SX was less than half the price of any of them. The 200SX may well be quick, but it isn't even 10% as nice as any of the others.
The Monza is bigger, cooler, more capacious and more stylish than a cheap four pot turbo'd Datsun coupé. It also has four full size seats and doesn't look like it must belong to a chip shop cook trying to be bling.
The BMW is elegant and has style that no 200SX can dream of. It's a bona-fide classic saloon car. (The 3.0 coupé is a properly useable four seater tourer with proper racing heritage)
The Rover is a four door saloon car with lots of interesting design features, an excellent ride, a classy interior, V8 engine and four seats
- all things the 200SX doesn't have.
The Capri 2.8i is heading into proper classic territory, hence values going up. The 200SX is heading into "very old Jap crap" territory, hence prices still going down.
Basically, the 200SX doesn't have space, class, good looks, race heritage (tramp drifting doesn't count) or any redeeming features other than a bit of poke and RWD. It's tuneable, but frankly I wouldn't be bothered, it's still an old Jap wannabe Capri and always will be. Loser.