Start with a couple of one liter bottled waters, cost $3-4.
A cheap fleece blanket in a hideously bright color, $7-10
Enamel camp cup, ~$2
Hot chocolate packets, probably free from me.
Bic lighter, ~$1
2 Trash bags, probably free from me (taken from the dorms).
Flashlight, ~$10

Total $23-28

This gives my friend water, shelter from cold and rain, light and a fire. Plus they can make themselves hot chocolate to stay calm and help stay warm. They can signal with the flashlight at night or the hideously bright colored blanket at during the day. This would be okay for a short summer day hike. In the winter, I would be hesitant about them being out with just this stuff. But then I don't usually see people carrying what they'd really need to spend the night in winter, and this is better then what most people carry on a day hike. I'd also assume we're carrying food, since I almost always like to stop for lunch or a snack on a day hike and always have food left over. Not necessary if you're stuck, but a great psychological boost if you do have it.