Yep, that's how it goes when you finance through the dealer. I did the same thing for my new (to me) Ranger. It's a contract that says you pay this many dollars for this many months. Double the payments and you cut the time in half, but you don't get a break on the interest. Which doesn't leave much motivation to pay it off early unless you just have the cash laying around...
I don't mind the fact that I'm overpaying for my truck due to the interest because I didn't buy my truck so it could make me money (directly). I bought it because I needed a vehicle that I could hopefully run to 200,000 miles and beyond without a major failure. Any vehicle you have to take a loan for is already a bad investment financially. As was the $1000 warranty you got. My only regret was taking the 72 month loan instead of the 60 month loan. Next time, if I can't easily afford the 48 or at least 60 month loan, I won't buy the vehicle. Lesson learned.