I am using commerce kickstart 2. Here's a screen shot of my product display
I've set a VAT tax rate in Drupal Commerce, so the price in that screenshot is the price of the product, plus the 20% VAT tax.
How can I display the price excluding VAT?
You should use Commerce Extra Price Formatters module.
Extra Price Formatters Implemented So Far
RRP / Your Price
Allows you to display the Retail Price and the User Price for a product and optionally the amount the customer will save.
Allows you to switch the display back to a single price if there is no discount available on a particular product.
Formatted Price with Prefix and Suffix
Allows you to present a price in the style just £9.99 ex VAT or only £9.99 for a limited time only.
Formatted Price with no decimal places
When you are selling items with whole unit prices, you don't necessarily want to see £10.00. This formatter lets you change the display to show £10. (use this with care!)
There's a video demo here: http://www.youtube.com/watch?v=-WR3mKjou8M
Then you should add two price fields in your product content type. In your manage display tab you would be having a settings option to calculate your price excluding or including tax and other parameters and thus you can add two price fields.