i had a mitsubishi magna that lost 5.5k in 18 months , i dont think you really grasping the concept of a depreciating asset
in comparison to crap aussie cars like magnas and falcadores they actually have good depretiation . my brother has a vt v8 commodore and that thing has dived in the last year or 2 , worth 11-12k tops . some imports like manual 34 gtts , TT supras and nice 32 gtrs have been going up a bit in japan recently as there quite sought after.
I sold a 95 sedan for 14.5k a year and a bit after I bought it for 14k . i had spent a bit on it , fmic , xforce exhaust , powerfc but those sorts of mods dont really add much and there just for enjoyment more than anything so dont add 15k your buy price and think thats what its worth with 15k of mods.
problem i think was you might have asked a little to much originally , you can get really nice s1 94-95s here at dealers for 15-16k with a warranty , all just detailed , paintwork fixed , dents taken out , new tyres , brakes etc . so really you should have started at about 14. 13-14 is a good price for a price s1 if its in good condition which yours may or may not be . some peoples idea of good condition varies greatly with mine so....