are those the sport mirrors bobo?

 

What is the reason for the cost difference between just springs vs coil overs? And performance gains. I assume coil overs must offer more/better improvements since they cost much more.

 

My mirrors are in option in switzerland... it's very beautiful !

 

The reason for the difference in price has to do with a few variables.

1) coilovers are a complete spring/ shock unit
2) coilovers usually offer features like ride hight adjustment, damping adjustment for rebound/ compression, while allowing full wheel articulation (travel).
3) some models come with camber adjustable top mounts (not RX8 unfortunatly)
4) coilovers usually save weight over the stock set up

-also, coilovers are easier to install than springs beacuse its a complete unit. Springs are a cost effective way to lower the center of gravity and increase handling charactoristics, though they offer no adjustablility.