The Hybrid pump will eventually fail, typically between 120k and 180k on both GS450h and LS600h cars.
But, it is not actually the pump that fails, it's just the two ball bearings within the pump which fail, preventing the shaft from turning. These bearings are about £7 each and are readily available from most bearing suppliers. The only down side is that it takes about 6 hours labour to change them, but it is a straight forward repair, so anyone with ramp can do it.
See my post "GS450h loss of power" for more detail.
Any local garage should be capable of doing this using my instructions, but unfortunately, Lexus don't repair vehicles properly, they only replace faulty parts, so avoid at all costs as you will be in for a £4-5k bill instead of a £500 bill !!
My point being; don't let the pump put you off. These are wonderful cars.
Incidentally, mine has 162k on the clock now and still drives like new. Save yourself £3k and go for the higher mileage car; after all, it is still low mileage!!.