Just bought an rx350 that was supposed to have the backup camera which it does not. Can the dealer install this item or should I bargain for a reduction in price??

Does the car have nav? I'd assume no, because i'm pretty sure the back-up cam comes with nav.

No I didn't get the nav, the back up monitor was a stand alone option that listed for 350.00 I think. When we agreed on the price my options were Premium Pkg, Heated seats and the backup monitor.

FWIW: When I bought my (new) 09RX350, I was told the camera came with the nav. package, but was unavailable otherwise. I have since had (rear) parking sensors installed. They work fine, indicate the distance (in inches) to contact quite accurately, and cost $190 incl. install.

The parking sensors that you had instaled...were they Lexus or after market. Lexus dealer do the install? As I ordered my 2010, this is something I couldnt believe Lexus has not included, even more that they have the back up camera. Even my Ford F-150 has both the sensors and camera.

They were not "Lexus" sensors, because I had read that one could not get/have installed parking sensors by Lexus. It happened by chance, when I had bought an "Autotronic" (or some such catchy name) that one attached to the bottom of the license plate, and performed similar functions. I installed it, but did not want to undo the various upholstery items needed to feed the buzzer into the cabin on my convertible BMW: I thought it was simpler to go to an (auto) alarm installation place since they would know the routing etc... As I waited to pay when they completed the work, I noticed they sold a 'set' of 4 'back' (and also a set of 8 for front and back) sensors. They make the holes in the bumper skin, install etc... for the $190 (which beats $490 that a friend paid to Ford, and the $1,400 that a friend refused to pay at MB!). However, the sensors come in black, and they (over)-charged me $100 to have them painted the exact colour of the car, so my total cost was $290. [If the car is black, no painting needed; if it is a 'simple' colour, a Dupli-Color Spray would cost +/-$5.- and take care of the job]. Very clean install, they look fine on the bumper and the display on the inside (which they set just under the base of the windshield, in the center) is perfect. The only gripe I have is that, when you move from P to D, the buzzer 'chirps' then emits a 'dying chirp' that bugs me, a very minor inconvenience. Had I know they offered them, I would have had then installed in the BMW. I find the overall price remarkably low. The alarm installers are called "AutoTech" here in Miami.
Sorry for the length of the post. In summary, I would suggest seeking out some alarm seller/installers and checking out the products they offer. On the other hand, if Lexus accepts to install, why not?
Good luck!

Our 2010 doesn't have "Nav" package but nevertheless has backup camera. I would ask for price reduction. Just as an aside... I decided against Nav system because a new fully loaded Garmin comes with Blue Tooth, Audio Player, newest maps, Traffic monitoring for life, rerouting, lifetime map upgrades $120, installed camera, Lane Assist, and plenty of other features plus it can be used on multiple vehicles or placed in pocket. No, it isn't as pretty as the built in system but seems like a better deal than paying 4 grand for one as the Garmin was only $369 or so online.

No 'clunky' Garmin after-market GPS system in my RX 350, and no, I didn't pay '4 grand' for it either. My Lexus nav system has all the features you noted for the Garmin..