There is no average amount. It depends on what you are suing for, what court you are in, and to some extent state law. A small claim of a couple thousand $$ can be filed by yourself in small claims court, and might only cost $50 to file. A million dollar lawsuit for negligence could be handled by a lawyer for free, for a % of the damages (anywhere from 25 - 60%) , if she thinks you have a good chance of winning. Most cases I handle I charge my clients by the hour, and it can cost anywhere from $10,000 to $50,000 by the time it's all over.