Assigning a value to a Google Analytics Goal allows you to do which of the following?
Analyze the conversion funnel on your website.
Track actual revenue from your conversions
Compare goal conversions and measure changes and improvements to your site
Track real-time revenue for your business
Assigning a monetary value to a goal gives you a way to compare conversions and measure changes and improvements to your site or app. All goal types except Smart Goals let you assign a value during the setup process. There are special considerations when setting up an Event goal or a goal that involves Ecommerce Tracking.
Read more here: https://support.google.com/analytics/answer/1032415?hl=en