I dont think the plastic is any worse than others out there, i think the only thing that "lets the car down" is the use of e-clips, i think it makes the car look retro and that because it doesnt look "modern" due to the hinge pins not being captured people are put off...
Its the small things people notice and nit pic at! IMO
I hate e-clips but i put up with them because the car is brilliant!
Re your car... I sold my old car recently with some spares and a new shell, it had been fully rebuilt with new wishbones etc... I asked £80 and got my hand bitten off! I think a clear shell helps so people can paint it to there scheme...
Try asking £70 ono and see what you get