Used cars have been remarkably valuable in the wake of the 2008 financial crisis, but prices are now starting to fall. That's good news for used-car buyers, who will pay less for a new (used) set of wheels.

Used car resale values first shot up in 2010, when prices jumped 20 percent in the first half of that year, according to Black Book, which tracks both the wholesale and retail values of used vehicles. Since then, prices have increased or held steady.

The price increase had a lot to do with slower car sales -- when sales plummeted to 10 million a year in 2009 from 16 million a year, dealers had fewer people coming in with trade-in vehicles. So they had fewer trade in cars to sell at auction, and used car prices began rising.

Now that trend is reversing. USA Today reported that overall used-car prices fell 4.5 percent on average in April. The biggest largest decline was in the minivan and crossover categories, both falling an average of 10 percent in wholesale price. Cars were down 6.6 percent. Full-size pickup prices rose 3.3 percent while full-size vans were up 8.1 percent.

If you're in the market for a used vehicle but can't find the deal you're hoping for the best thing to do is wait for the trend to continue downwards. The rise of new auto sales in the last year means that newer used models should be hitting dealerships shortly.