How do you ship chocolate so it won't melt, in the least expensive way?
If you are shipping chocolate in warm weather, it's probably best to ship it overnight. It is not the least expensive way to ship, but it will give you the best chance of having it arrive in tact.
If the weather is cool, you shouldn't have to worry much about the chocolate melting.
Just wrap the chocolate well and also use some type of protective layer, like bubble wrap, scrunched up newspaper, air popped popcorn, or Styrofoam pellets.
Some companies will add an ice pack or cold pack when shipping chocolate.
If you decide to try using a cold pack yourself, be sure that you have the candy in an inner package that won't be affected by any moisture that occurs from condensation, etc. You may want to place the container holding the chocolate in a Ziploc bag.
Finally, use a sturdy outer box for shipping and you should be fine. :)