What @Syntax_Error had said is correct you have to use get_price(), WooCOmmerce also provide a wrapper function wc_get_product() for WC_Product class.

So your function would look something like this:

function add_price_widget()
{
    $product = wc_get_product(get_the_ID());
    $thePrice = $product->get_price(); //will give raw price
    echo $thePrice;
}

Hope this helps!

You can just use the function get_price that returns only the number (without dots or symbol)

function add_price_widget() {
 global $woocommerce;
 $product = new WC_Product(get_the_ID()); 
 $thePrice = $product->get_price();
 echo thePrice;
}

I just tested it in my site and it work. So it should work for you too.