Same thing happened with me! But not in Sapa. I got to Hanoi from a train coming from dong hoi. I got into a taxi that said he’d go by the meter. We get to my hotel which was 2.2 kilometers from the train station. The meter is 480,000!!!! I told him I know he’s scamming me and it’s not the price because in a different place for 2 kilometres I paid around 80.000. Anyways after arguing with him he lowered the price to 300.000. They’re lots of fake taxis here in Vietnam. I think theres like two company’s that are actually real company’s.. forget the names but you can find the names easily online. Only ride with them! Also another thing I noticed about this taxi was the guy was in regular clothes and didn’t have his ID shown like the other taxis I’ve been on.