The bounce test for shock absorbers is very hard to do on modern cars and especially so with the RX being a big heavy car.
I noticed on the lexus website front shock replacement cost was £400, but I wasn't sure if that was for just one side, which I think it probably is. Still in the end I bought new shocks, springs, strut mounts and bearings for both side for £300 and have just finished fitting them myself. Only been on a short drive since, but car feels transformed, especially as no more dipping when braking hard.
Heavy components, but one of easiest cars I have worked on, quality of construction was obvious.