Used vehicle sales are soaring these days, and so are their prices. Though it tends to counter the conventional wisdom that only highly valued collectible cars ever increase in value, Edmunds.com reports that used car prices jumped by 7.6 percent in the second quarter of 2015 to reach a record average high of $18,800. While this tends to make bargain hunting among late-model pre-owned models difficult, there’s one segment of the used-car business that’s actually…