Texture Quality - Performance for Mobile Devices

I have tried 16 bit color and no larger textures than 256x256 and reduce the tris to no more than 12k and I still have performance issues with iPhone 3GS devices. I have also replaced almost all the Update functions with co-routines, no shadows and not to many objects on stage simultaneously and what I have earned is a few more frames per second. The resolution is exactly the same as my 3GS; and all that for nothing!!! I strongly believe that Unity is not playable on older mobile devices as other engines are. Compare games like the "Race after 1977" or "Drift mania" and you will see what I mean. If there is any other magic trick I can make (like buying the Pro version?) please be so kind and tell me.