is it possible to set product price base on rules

I try to set node->price = node->list_price * 0.7.
when i output node->price in node template, th value has not been changed by rules.

List price: 29.80
sell price:19.80

I output it in node template using following code:

print $node->price;

It seems that "$node->price;" is not been changed. it display: 19.80.

If I using following code:

print $price;

it display: 20.86.
It is correct.

I think that $node->price and $price should keep the same at here. But they are different in node template.

In uc_product.module, function uc_product_view,
Add following code

  foreach (array('price', 'model', 'list_price', 'cost', 'sell_price', 'weight', 'length', 'width', 'height', 'length_units') as $property) {
    if (isset($variant->{$property})) {
      $node->{$property} = $variant->{$property};
    }
  }
 

below :

$node->content['dimensions'] = array(
    '#theme' => 'uc_product_dimensions',
    '#length' => $variant->length,
    '#width' => $variant->width,
    '#height' => $variant->height,
    '#units' => $variant->length_units,
    '#view_mode' => $view_mode,
  );

could fix this issue.

A lot developers use

  print $node->price;

instead of

  print $price;

It better to write some document about this:
$node->price maybe different with $price.

It looks very strange that in rules I changed the value of $node->price, but in node template, $node->price has not been changed.