Mate to have this car serviced quaterley aint pricey lol.
I got a 93 with 280k on the clock, and i service it every 3 months for around the $300 mark, which includes oil filter with oil change, fuel filter, air filter, spark plugs, radiator flush and engine flush. Dont take your car to Lexus to get it serviced. I service my car myself so i just pay around $140 for the gear.
Timing belt can be fitted between 250 to 350 mark. Depends when everything was last changed. I would doubt there will be anything wrong with the timing belt. The most common cause for the ES series is that after a long period of time the gearbox goes on its way.