Jim, the figures by celeriter are pretty accurate for a simple facility. (in my opinion)
Things to ask yourself though are about drainage and surface. If you go with a simple surface like latex with a structural spray, you'll get a track that's high school ready. But the drainage is a major issue. What will you do with the inner surface?
The asphalt is the real issue though, and more importantly, making sure that it fits in to the 2% grade requirements. We had a lot of trouble getting a contractor to do our facility, because the college facility requirements are tougher.
I don't know why you'd beleive that wider turns would make it cheaper... Turns require more area for the distance, and area is not your friend.
Jim, for the record, we just finished out facility. We spent $2.5 million. But we went top notch with everything, surface, inner surface, drainage, and all.
Three years ago the university across town built a track, probably similar to what you're thinking of. It was literally a track, and nothing more. No "D" area, just 8 lanes. They tore it up a little while ago, because it didn't fit their needs. Make sure you're planning for the future too.