chadsmith

Requires approval on comments from non-registered users that contain an author URL.

Moderate if author URL

Requires approval on comments that contain an author URL.

Chris Allen

Poodle Plugins

This plugin will allow you to completely customise the empty price HTML on a single product page. It can be used to add a ‘CONTACT FOR PRICING’ call to action button, 
some advisory text, or any custom HTML you choose.
There are three ‘content types’ available for flexibility & ease of use:
<ol>
<li>A simple text box with options for bold or italic styling</li>
<li>A button with an optional link</li>
<li>An option to add your own custom HTML</li>
</ol>
By default it will use the styles available in your custom theme, but each content type has a configurable CSS class, should you wish to style the content further.
Note on variable products:
The custom content will only show on variable products if none of the variations have a price set. Due to the nature of variable products, this will result in an out of stock message being displayed. If you do not wish to have this out of stock message, the simplest option is to only use this on ‘Simple’ or ‘Grouped’ products.

Custom Empty Price for WooCommerce

Show text, a call to action or custom HTML when a product has no price set.

Moderate if author URL vs Custom Empty Price for WooCommerce