What is the best way to protect my business name from being copied? How do I avoid paying through the nose to do so?


The good news is that both copyrights and trademarks receive protection automatically upon creation (in the case of copyrights) and established use (in the case of trademarks).  However, in the real world, having “ownership” means very little if you can’t protect your copyright or trademark from infringers.  So even though registration of a copyright or trademark is not required, there are distinct advantages to doing so.  
For copyrights, timely registration establishes a public record of ownership and enables an owner to collect both statutory damages and attorney's fees (as opposed to just actual damages and lost profits, which may be hard to prove).  For trademarks, securing a federal registration is highly recommended because it established priority and provides exclusive rights to prevent unauthorized use of the mark nationwide.  It also creates a legal presumption of ownership and enables owners to sue for infringement in federal courts.
As mentioned above, the real benefit of obtaining either a registered copyright or trademark is that it helps the owner AVOID court by providing him or her with a more powerful threat to use against potential infringers.  Specifically, the threat of a streamlined, relatively inexpensive litigation if the infringing material isn’t removed, credited, licensed, or otherwise dealt with in the manner required by the owner.
Of course, not all business or product names are trademarkable. For example, your trademark should not contain only words or symbols that are already in common use (i.e., Aspirin) or that are overly descriptive of your goods or services (You can’t trademark “Soda” as the name of your new cola beverage).  Finally, your desired trademark (or something too similar to your desired trademark) may already be taken by another owner.  For this reason, it is a good idea to conduct a trademark search before attempting to file a trademark application.