JP250

So my 2008 IS250 AWD (123k miles) was just diagnosed with a bad brake booster. I got a quote from a shop saying it is $657 for an OEM brake booster from Lexus and $250 for the labor. I called Lexus and they said the repair would be $1,187 plus tax. The service advisor on the phone thought it was odd that the brake booster went bad and that they usually never replace those out. So is it possible that the brake booster is actually good and there may be a possible vacuum leak? mMy car does have 123k miles, so maybe thats normal? anyone know how i can check for a vacuum leak? or check if the booster is fine and maybe just needs a hose replacement? I have a small feeling that this shop is giving me a run for my money.

The price for this repair is pretty steep for me and it especially doesn't make me feel good that brake boosters are rarely replaced. I saw a few used brake boosters online go a low as $70 all the way to $150. I can't believe a brand new one is $650! Anyone run into this problem?