The cost of a professionally designed and installed LED system varies depending on various factors, such as the size and complexity of the system, the type of LED lights used, and the location and accessibility of the installation. Generally, the cost can range from several hundred to a few thousand dollars for a basic installation with standard LED lights. More complex installations or custom designs can cost significantly more. Getting a detailed quote from a reputable installer is important to get an accurate estimate of the cost for your specific needs and budget.