The most expensive floor in a house in the United States is typically the highest floor. This is due to several factors that contribute to the increased value of high-rise homes. Firstly, the panoramic views offered by higher floors are highly sought after, as they provide residents with unobstructed vistas of the surrounding cityscape or natural landscapes. According to a report by the National Association of Realtors, homes with views can command a premium of up to 10% over similar properties without such views.

Secondly, the scarcity of high-floor units in many buildings contributes to their higher price tags. High-rise buildings often have a limited number of units on the upper floors, making them more exclusive and desirable. This exclusivity is a significant factor in the premium pricing for these properties.

Additionally, the amenities and services available to high-floor residents often contribute to their higher costs. Many high-rise buildings offer luxury amenities such as rooftop pools, fitness centers, and concierge services, which are more likely to be found on higher floors. These amenities add to the overall value of the property and justify the higher price.

Data from the Zillow Home Value Index supports this trend, showing that homes on the top floors of high-rise buildings tend to have higher median sale prices compared to those on lower floors. For instance, a study by Zillow found that in New York City, the median sale price for a high-rise apartment on the top floor was $1.2 million, while the median sale price for a similar apartment on the ground floor was $950,000.

In conclusion, the highest floor in a house is more expensive in the United States due to the superior views, scarcity of high-floor units, and additional amenities and services offered to residents. These factors collectively contribute to the premium pricing for high-rise homes on the upper floors.