Clutch chatter... cause and correction?

[epapp]

I too found much cheaper alternative clutch/flywheel parts than what I was quoted. Mechanic said he wouldn't mind putting them in but he could not warranty something he did not vouch for/know very well(said he only sticks to genuine sachs). I agreed with his reason. If I was running a shop, I would not like to risk putting my warranty on a part from a vendor I didn't know well.

EDIT: I'm sure his shops profit margin on the parts played a role in his reasoning, but the fundamental reasoning was still there..