i've been quoted $750 for a new flex pipe and cat converter (2.25)
Whoa!!!
3 years ago i had a 2.25" system put through my car. That included a brand new high flow cat, a nice long resonator in the middle and a straight through muffler at the rear with a 2.5 inch chrome tip. Total cost was around $600 (give or take $50, can't remember exactly...).
I didn't have any flex pipes replaced, but i don't imagine that the flex pipe would be worth hundreds.... (unless you are buying genuine parts).
So yes, i think that $750 is a total rip off! Keep shopping around... Which State are you in?
Dan.