Expected Revenue Question

Expected Revenue Question

Is it possible to keep the expected revenue static and not change throughout the sales cycle?

I cannot seem to grasp the mindset behind the revenue changing based on probability. A $50,000 revenue deal is not worth $5000 today at the inquiry stage, and $25,000 half way thru the sales process. It is worth zero until it is Closed Won, at which time it is worth $50,000.

Am I missing something? I can understand the tracking of probability of the deal thru the sales process, but not affecting revenue.