My flight will arrive at Hangzhou International Airport at 11 pm night

Yes, the taxi fare is charged by meter rate during that time. According to the group members, you need two taxies. If you want to take the taxi from the airport to the Westlake Area, the fare is CNY 120 to 130 per taxi, because the local taxi only have three seats. You need a five seat car.

So you can take airport shuttle bus line (Airport → Wulinmen CAAC Ticket Office), and get off at Wulinmen CAAC Ticket Office first. After arriving, just take a taxi to the scenic area of the Westlake. In this way, the taxi fare is CNY 15 to 20.