Cost effective: 
You will save a lot money and time by doing your own web site.  A five to six pages of web site will cost you hundreds if not thousand of dollars.  Later on, you also have to pay fees for updating information. 
In addition to money, you need to work with the designers as a team.  In other words, you have to spend time on assisting the designers and training them to know your business.
You will also spend more time on gathering information, explaining your business, your marketing strategy, and goals of your web site to the designers.  Searching for a good layout of your web site, and approving the final contents are your jobs too. 
Your web site won't come out right unless you are a part of this creation.  Eight months ago, one of the gallery owners told me that they would have a web site pretty soon.  Last Oct. I met their designers at the art show.  They are still waiting for the information and pictures from the gallery. 
In addition to helping the third parties do your web site, you need to understand the busy workload of designers.  Their schedule might not fit in with your deadline for web site promotion.  Also, if new staff takes over the job of your web site, you will have to start over the training process with that individual. 
At the beginning, it will be difficult to do your own web site if you plan to write HTML.  However, you can use a software, such as Microsoft FrontPage 2000.  After you gain some practice through the software, you will love it.          
                                            ------to be continued.