Daily Sale offers this Peel and Stick Self-Adhesive Chalkboard or Whiteboard for $8 with free shipping. Outside of the mention below, that's the lowest total price we could find by $2, although we saw a similar self-adhesive chalkboard for $2 less three weeks ago. It measures 79" x 18", sticks to most walls, and includes chalk or a dry erase marker, depending on your selection. (Note: The countdown timer on the product page does not reflect an actual expiration time and resets daily.)
A close price: Corydor via Amazon offers the similar Con-tact Self-Adhesive Chalkboard Liner for $7.75 with free shipping for Prime members, but no chalk is included.