woothemes/woocommerce — pull request #1582 by helgatheviking (2012-10-09 20:25:38+00:00)
Title: Don't delete _regular_price (et al) for custom post types

Perhaps I should be using a simple product type, but I think I need to create a custom one so that I can integrate WC with [EZ Prints](http://www.ezpservices.com/)' product customization and fulfillment. Anyway, I found that the price meta is reset (set to a null string) if the product type is neither simple nor external and I found myself having to re-produce this code to get the data to save.

Instead, I added this filter which will let the existing code run for my custom post type.