Patent valuation is really slippery, and completely depends on the context.
Patents can be thought of as call options on technology. They are a time-limited bet that the market will adopt a technology.
At the beginning, the patent is an out-of-the-money call option and has only potential value. Once infringement occurs, the patent turns into an in-the-money call option, since we now have some basis to recover licensing fees.
Sky-high valuation numbers that come with many patents are terribly unreliable.
The only valuation that is trustworthy is one where someone is writing a check. Anything else is pure speculation.