How to use Webform's summed result in another node or block?
It is kind of confusing to create Webform Views with aggregation at first, I'll try to give a detailed explanation.
First, you would create a View of "Webform Submissions" - use unformatted list of fields as format.  

Remove all fields that are placed in your View by default.  

Add relationship to "Webform Submissions: Data" as shown the screenshot below. Adding relationship to webform submission data is crucial for Summing up your field values, because the added relationship gives you an option to add raw value of your field to the View (otherwise SUM aggregation doesnt work - see here). So, you would select your Webform node by typing its ID or the Name of your form, then in "Component Data" drop-down you'll select the field which stores the number that you need to sum up. 



Add the field to the View scope:
Select "Webform submission data: Numeric value(raw)", or " *: Value(raw)". They both will produce the result that you want.  Make sure you select the relationship that you added previously in the field relationship drop-down.



Enable Aggregation for your View and set Aggregation to "SUM" on the your numeric field. Watch your field result summed up. 

See if this approach works for you.