For a less ridiculous hypothetical, we know that BBRY has $3bn in cash right now. Supposing that it instead had $10bn in cash, its valuation would not be the same, it would be $7b higher. Its stock price (and equivalently its market capitalization) would reflect that, because the stock market is a place where people who disagree about the how to value the company go to make trades they believe are favorable. People who go to the public markets and act on the belief that ($10b in cash + a niche mobile phone business) should be valued at $5b would be rare. They would also be very wrong.
The current valuation of $5b implies that the niche phone business is worth $2b and the $3b in cash is worth $3b.