Well you know people have been buying cars without tax deductions for decades ;)
I looked around and the RX400h isn't going to be recieving any of those things anyways because it isn't going to have good enough fuel economy. It has to get 50MPG and they're thinking 40 highway, so it will even have to be emissions tested unlike the Prius. But still 40 highway for an SUV with V8 performance? Why is a tax deduction neccisary to get in on that? The RX330 gets maybe half that on a good day, you're cutting your gas bills in half! Plus I would buy it just to have the "higher version" of the RX which Lexus is counting on also.
And I trust Lexus' opinion on the pricing they're saying that the 400h should be around $1500 more. They sell the Prius for 26k with all the options it has (voice activated nav, smart entry, bluetooth, JBL stereo, Bizenon headlamps) what makes you think they can't deliver the RX400h which isn't going to have a lot of extra equipment over the 330 for only $1500 more? $5500 more wouldn't make any sense because it would price the RX400h way out of its price class.
The batteries actually cost $8,000 to replace. But just because the parts cost that much doesn't mean the car does. The 4.3 liter V8 costs almost $20,000 to replace, but the GS430 isn't $20,000 more than the GS300, its only about $2,000 more.