See this textbook which provides three standard methods of valuation. Available on Amazon.
"Valuation of Intellectual Capital and Intangible Assets," Gordon V. Smith and Russell L. Parr.
An interesting fact is that when one looks at SEC filings of public companies, many have stated valuations and specific balance sheet line items for "Intangible Capital" or similar. In some cases there are specific line items for such things as Engineering Drawings, Recipes, Customer Lists, and Noncompete Agreements, to name a few. This is real world IP/IC valuation completed by the companies' CPA firms. What are we missing here?