The transmission went out on my 03 RX300 at about 180k miles, which I thought was quite early for a Toyota made vehicle to be honest. Anyways, my mechanic told me 3700 for a complete rebuild and instead I ordered a remanufactured transmission after reading this article on the differences between rebuilt and remanufactured. Hope this helps
https://transmissioninfo.wixsite.com/transmissioninfo/rx-300