The Bushnell Elite 3200 3-9x is going for $130 from several places on-line (midwayusa for instance). I have one on my 30-06 and love it.

I may have missed someone else mentioning it, but there is the Rem 7400. I saw one in 308 for $510 a few days ago. I know they come in 243 as well.

I personally started all my kids out with 22 bolt guns. They are fairly cheap (I got a savage for $99 5 or 6 years ago), and ammo is a lot cheaper than centerfire rifles. I take them to the range and we learn basic gun handling and techniques first, then move to different shooting positions. I regularly use my 22 during range sessions as well - I have a flinching problem and it really helps me to fire a few groups with the 22 between groups with the centerfires.