datsun,
Stock clutch plates come with sprung centre hubs on the pressure plate, which dampens both noise and drivetrain vibration.
Aftermarket performance clutches normally use stiffer, fewer, or even no springs (solid centre hub), resulting in the decelleration noise and mild vibration (can be felt through the clutch pedal) while the clutch is engaged. Also, on multiplate clutches, the lack of centre hub damping causes loud clashing noises while the clutch is disengaged.
The noises and vibrations are normal for most performance clutches, and though irritating, does not harm either the transmission or the engine.
Just to let you know, the decel noise is present on the Exedy organic plate also, though I'm not sure how much quieter it is compared to the three-puck racing clutch.
I don't know how much the pressure plate alone costs, but I paid 1500 for the whole kit, which includes the plate, cover, and throw-out bearing.