Audi on Monday announced U.S. pricing for the R8 V10 GT, marking the swan song for the German automaker’s V-10 engine. The base price is $249,900 plus a $1,495 destination charge, $595 for paint, and a $1,300 gas guzzler tax. That brings the total cost to $253,290 for each of the 150 units planned for the U.S., out of 333 globally. The R8 V10 GT…