Budget up to £2,000. I don't suspect Lexus have changed their design, so if the bushes are worn, you have to actually change the entire control arm, as some of the bushes are pressed in, and you can't actually buy the bush separately from Lexus, you have to buy a new arm, which in the UK cost a huge amount.
Again, a dealer will say whatever they need in order to sell a car and make a profit. Many cars are serviced (which is generally oil and filter with and an inspection), but not all cars are maintained to factory spec. because some owners want to save cash. My personal opinion is to walk away from the car unless it has a paper trail to back up claims that it's been looked after, unless the price has been reduced to reflect no paper trail.
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Do set aside the funds for repair. I did not spend enough time researching a 1990 LS400 with 169,000 miles. Within the first month of ownership I have had to replace the power steering pump, the alternator (I got stranded on the highway), the steering rack, front brake pads, timing belt and lower ball joint. (Cost: $4600 USD or about 2400 GBP) Two different mechanics are also recommending front stuts and front upper control arms -- for approximately the amount I have already had to put into the car. But, since I haven't even had the car a month, I think I'll just hold off for a while -- maybe a long while.