I just got quoted $900 for cat removal and replacement in labor alone from Infiniti…..

 

I'd check with a few reputable muffler shops in your area as the dealer doesn't like to deal with cat removal and replacement as the cats themselves can also weld themselves in place and be difficult to remove.

I had one repaired under warranty years ago and it took them the better part of 3-4 hours to remove the old one.

$900 still sounds steep for labor alone.

Note that if you are not in CA, there are alot of replacement CATs out there that cost 1/2 of what the CARB approved CAT costs. Magnaflow is a good source for CATs (CARB and Federal approved) as well as they are higher flow and also cost a smidge less than OEM.

 

Average service fees at dealerships is currently $130/hour, so that's almost 7 hours in labor in your case. Basically, a full day of labor. That is kind of steep, but not entirely unrealistic. Cat removal on this car is a bear, particularly if they've been on the car for a decade. If it's an honest shop, they'll only charge you for the actual time spent, and not the full quote.

Go visit a couple of speed shops in your area. Get some quotes, network around.

Aftermarket high-flow cats would almost certainly be less expensive than OEM cats, and a performance upgrade as well. However, it's very, very unlikely your dealership would install aftermarket cats. So if you go that route, you're going to have to find an independent shop. Maybe one that doesn't do state inspections, if you get my drift.