Problem
The static price field is grayed out and can't be edited.
Solution
Enable Use Static Prices
Go to the navigation bar and click Pricebook.
In the side menu, click Services.
Click More >View/Edit Service.
Under the Details tab select Use Static Prices.

You can edit Price, Member Price, Add On Price, and Member Add On Price, if necessary.
When finished, click Save.
Note: If you use Dynamic Pricing and there is no price rule, static pricing will be used whether you check the box or not. See Dynamic Pricing for more.