In general, the more complex a business venture, the greater the valuation. The more complex a venture, the longer it would take to replicate it from scratch. And time is money! While most any venture can be replicated, it will take time and money to do so. Is it less expensive to start from scratch, or buy an existing venture? That's the essence of the thought process buyers go through before investing in (or, in essence, buying) a business.
Venture complexity may well come from a variety of sources. For example, brand recognition and reputation is an example of "complexity" that encompasses the blend of perspectives from industry, markets, customers, suppliers, employees, community, and more. While some brands do become "viral" relatively fast, most brands evolve over a significant period of time. Arguably, the brand is the only long term sustainable competitive advantage of any company. That's assuming, of course, that the company doesn't "screw it up"!