While May might not have brought the big uptick in sales we’ve seen in recent months, preliminary data suggest that automakers took in record revenues, with the average transaction price of new cars, trucks and crossovers sold last month climbing by at least 4%, reports The Detroit Bureau. 

All told, U.S. buyers spent a record $52 billion for their new vehicles in May, in part, due to a sharp, year-over-year decline in incentives, according to several firms that track monthly sales data. A separate study suggested that motorists are covering those higher costs by stretching their loans out longer than the industry has ever seen, an average 67 months.

“New vehicle sector and segment preference indicates consumers are confident about the economy and their finances,” said TrueCar President John Krafcik. “Not only are these shifts to premium brands and utilities telling from an economic indicator standpoint, they signal sizable revenue gains automakers should reap this year.”

The data tracking firm estimated that the typical vehicle had an average transaction price, or ATP, of $32,452, up 4% rom May 2014. Lower incentives played a role, but manufacturers have also seen buyers show more confidence by loading up on options and by trading up to higher-level vehicles. TrueCar estimated sales of premium brands jumped 10.6% during the first four months of 2015 compared to just 4.8% for mainstream brands.

BMW and its Mini subsidiary, saw prices jump in May by 6.5%, according to a separate analysis by Kelley Blue Book. Mazda saw a similar increase, while Ford and General Motors prices climbed a more modest 4.3% and 4.2% respectively. Toyota’s average price rose just 2.3%, even though it trimmed incentives by more than 10%, year-over-year.

With only a handful of exceptions, notably including General Motors, Hyundai and Kia, most makers trimmed rebates and givebacks as the U.S. auto market continued to gain ground. And analysts noted that the modest overall sales numbers for May actually misrepresent the market’s momentum, as the peculiarities of the industry’s reporting system counted fewer so-called “sales days” last month than in May 2014.

The surge in spending also reflects a year-long shift from fuel-efficient small cars and alternative-power vehicles to larger passenger cars, pickups and SUVs.

“With the national average price of gasoline down nearly a dollar per gallon on average from one year ago, truck and SUV demand remains strong, elevating average transaction prices,” Karl Brauer, senior analyst for Kelley Blue Book, said in a statement.

The steady climb in new car prices might come as a surprise to those worried about relatively stagnant middle-class earnings and the rising wealth gap. In reality, most new car buyers today register on the upper end of the middle-class spectrum. Even for compact cars, industry research often shows household income levels approaching six figures.

And buyers are simply stretching out their purchases to hold down monthly payments – while also encouraged by continuing low interest rates. Gone are the days of three and even four-year loans. Borrowers extended their loans terms during the previous quarter to 67 months on average, longer than ever for new cars, according to Experian Automotive.

“While longer term loans are growing, they do not necessarily represent an ominous sign for the market,” said Melinda Zabritski, Experian’s senior director of automotive finance.

On the plus side, the trend allows consumers to buy more vehicle without busting the household budget. On the downside, however, it means they likely have to keep those vehicles longer in order to avoid being upside-down on loans when trading in, cautioned Zabritski. That could foretell slower future growth of the automotive market.