If you got a refund, that is good news. I'll echo that these keys are nigh-on impossible to reprogram. I have a very good friend who is also a master locksmith and if he couldn't do it, nor any of his close associates, then yeah, paying Lexus an exorbitant amount is the only way I can think of.
Slightly off topic, but does anyone know the best place to buy a blank key? I only have one and although it (blank) won't be able to be used to drive the car, the blade cut to shape would mean I needn't worry about locking my key in the boot 😱