Hi,
The price of the variant replaces the price of the main product. So in your variants, you should enter the price including the main product price.
If you want that the prices to be separated and summed together based on what is selected, then you can use options. In that case, the product page will display the main product page, the price for each element of the option in the selection dropdown, and a total price which will be the sum of the main product price plus the price of the selected choice in the option dropdown.
However, if you use options, the stock of each choices of the option will be separated from the stock of the main product so you won't be able to see the stock of each choice on the product page.
To me, it sounds that the characteristics/variants system is more adapted to your needs than options and that you should just enter the correct price in each variant of the product.