The estimated average transaction price for light vehicles in the United States was $37,577 in December 2018, up 1.3 percent year-over-year. December closed out a very strong year for new-car prices, as they rose to more than $36,000 on average in 2018, a 3 percent increase. Despite higher interest rates and incentives remaining flat year-over-year, this was the strongest growth in transaction prices since 2013, according to Kelley Blue Book.