WooCommerce Variation Prices controls how the prices of your variable products are displayed. It doesn't change the price which your customers are charged.
You add your variations and set pricing as usual. WooCommerce Variation Prices then lets you choose how these prices are formatted and displayed on the front end of your website.
It works beautifully with dynamic pricing plugins which let you change variation prices, such as:
Dynamic Pricing - for adding dynamic discounts and bulk product pricing.
WooCommerce Bulk Variations - for quickly updating variation prices in bulk.
WooCommerce Attribute Swatches - for replacing the variation dropdowns with color swatches and images, and adding extra costs to certain attributes.