What's the fuel consumption of the Tahoe with a 2.7t engine? Approximately how much in the city and on the highway?

Around 12 in total, give or take a little.

Do people still consider fuel economy when buying a car worth 600,000?

Bro, who cares about fuel economy when buying a Tahoe? Maybe you should check out the Leopard 5. It's fuel efficient.

It's about 12 liters per 100 kilometers on average, I've asked around.

This weight, 18 in the city is normal, 12 on the highway is normal.

Combined fuel consumption is 19 MPG, which translates to around 12 to 13 liters per 100 kilometers.

I guess the average fuel consumption is between 11-13, in the city it's 15-18, and on the highway it's 9-10.