A mail piece is worth ten times its weight in gold if you write a good one. The piece should be concise and informative about your company. It should be devoid of all the corporate jargon that makes most people yawn. It should grab the readers attention from the first line to the last.
If you cant afford to employ professionals to write mail pieces then the best person to do it is you. You as the owner of the company know more about it then anyone else. After you have written it, have someone else look over the typos and grammatical errors. Ask a couple of other people in the company who have writing experience to see if you have written an effective piece.