php - How to change Woocommerce price?

function regular_price_func( $price, $product )
{
    //your logic for calculating the new price here
     $price = $product->get_regular_price()*1.3;

    //Return the new price (this is the price that will be used everywhere in the store)
    return $price;
}
add_filter('woocommerce_product_get_price', 'regular_price_func', 99, 2);

Solution:

Try this, You can change the sale price and regular price and update the condition accordingly.

//Change/Update Regular price 
add_filter( 'woocommerce_product_get_regular_price', 'regular_price_func', 10, 2 );
add_filter( 'woocommerce_product_get_price', 'regular_price_func', 10, 2 );
add_filter( 'woocommerce_product_variation_get_regular_price', 'regular_price_func', 10, 2 );
function regular_price_func( $regular_price, $product ) {
    $rate = 1.3;
    if( empty($regular_price) || $regular_price == 0 ){
    return $product->get_price() * $rate;  
    } else{
    return $regular_price * $rate;  
    }
    
}

// You can also Change/Update Sale price 
add_filter( 'woocommerce_product_get_sale_price', 'woo_sale_price_price_func', 10, 2 );
add_filter( 'woocommerce_product_variation_get_sale_price', 'woo_sale_price_price_func', 10, 2 );
function woo_sale_price_price_func( $sale_price, $product ) {
    $rate = 1.3;
    if( empty($sale_price) || $sale_price == 0 )
    return $product->get_regular_price() * $rate;
    else
    return $sale_price * $rate;
};

Solution:

If you're looking to alter either the regular price OR the sale price. You have to specify which ones you want to use.

Also, the hook woocommerce_product_get_price is deprecated as of 3.0, the replacement for this is woocommerce_get_price - and finally, this filter returns price as a string, so to multiply a value, you need the floatval of that string.

function regular_price_func($price, $product) {
    if ($product->is_on_sale()){
        $price = floatval($product->get_sale_price()) * 1.3;
    } else {
        $price = floatval( $product->get_regular_price() ) * 1.3;
    }
    //Return the new price (this is the price that will be used everywhere in the store)
    return $price;
}

add_filter( 'woocommerce_get_price', 'regular_price_func', 99, 2 );