2009 Trek Madone 5.5 – retailed for 4600$ back in the day. Is it worth 870$? Bike market is inflated where I live

Not worth $870, probably closer to $400-500.
It’s a 15 year old bike. Quite a nice one though. Although you definitely would be needing new bar tape, it looks pretty ragged on that bike. And those hoods need a thorough disinfection. Those white ones aren’t stock so I would wonder if the bike maybe had a crash requiring the hoods to be replaced.