Publicized statistics often peg the median cost of a patent lawsuit at hundreds of thousands of dollars (for cases with less than $1 Million at stake) to between $1 million and $2 million (for cases worth more). So being served with a complaint alleging patent infringement can certainly raise alarm bells at any business.
The truth is, however, that many patent infringement lawsuits can be resolved for much less. Some plaintiffs, particularly non-practicing entities, may just be looking for a one-time licensing fee that is far less than the cost of litigating. Trying to find out what the patent owner wants is often a good way to gauge the seriousness of the exposure.
If the case cannot be resolved quickly or efficiently, then the strength of the infringement claim, as well as the potential damages, will need to be analyzed. There may also be ways to challenge the validity of the patent (despite the fact that the PTO granted the patent in the first place).
After the foregoing analysis, a business that has been sued for patent infringement can develop a defense strategy and budget.