Default value for Price field
It is not possible for the default price field, because Drupal locks down the field / widget settings for "locked" fields. This is a general Drupal issue, but you could work around it by using an alternate price field that you add custom to your product type paired with a product pricing rule that swaps that price in at the start of the pricing process. You'd have to do a form alter or something to hide the default price field from your product forms.