Well, not sure what to suggest here, but allow me to make a few comments:

Your mileage will improve a little bit with time. The engine/drivetrain needs breaking in, and the trolling resistance of the tires will decrease with use, although most of those effects occur during the first 2k miles.

Next, your salesperson had it wrong, if the EPA mileage testing/reporting will change to reflect more realistic actual use conditions, EPA mileage - especially for hybrids - will go DOWN, not up! Also, the manufacturers - including Toyota - would very gladly report more realistic mileage values, but they are not legally allowed to report anything other than EPA values, even though we all know how bogus those numbers are. These numbers are derived by following the EPA guidelines, so the fault for the discrepancy between EPA values, and real life values, lies not with Toyota IMHO, but with the EPA.

Third: the physics don't change, and people should not expect miracles. Mileage is still and will always be primarily a function of two parameters: mass of the vehicle, and drag (wind and rolling resistance). Both of those are much worse for most SUVs, than smaller, lighter, regular cars. SUVs will always get worse mileage than cars, there is no way around that. In fact, small, lightweight regular non-hybrid cars (Honda Civic, MINI Cooper, etc..) will probably always get better mileage than even hybrid SUVs, because of inherent mass, size and drag advantages. But, hybrid SUVs will be slightly better than non-hybrid SUVs.

The consolation for you may be that your RX400h should get better mileage, than a non-hybrid one under similar driving conditions. As others have posted
(see also: http://www.greenhybrid.com/discuss/i...eeks.2654.html )
with a hybrid, mileage is also a function of trip length. Short trips will absolutely kill mileage. Tire pressure, driving style, temperatures, gas type, etc.. all will have effects.
The bottom line is: in a non-hybrid Lexus RX you would probably get worse mileage. And, there is only so much hybrid technology can do for an SUV.
I would say that if you absolutely have to have an SUV, then it's still great that you got a hybrid, because you will have less impact than with a standard SUV.
You will not recover the additional cost, but you are still doing something good compared to standard SUVs, and you are promoting this technology, and that is great! In my 05 Prius, I also don't get the EPA listed mileage (I'm averaging about 45mpg instead of the EPA average of 55), but I am very happy about it, since that is much better than what I could get in another car that meets my space needs (and of course I could do even better in an Insight, but it's too small for me).

Cheers,
M