Is there a hook for custom line item before rules price calculation? I have a complex calculation for item price in a custom line item that I'd like to keep in code rather than rules. Is there a hook that gets called before cart calculation so I can set unit price? 

Where is cart pricing calculation done in commerce? trying to find where it's run in source.

Drupal 7 (using kickstart 2)
As Clive mentioned, there's hook_commerce_product_calculate_sell_price_line_item_alter() that lets you manipulate the line item prior to the sell price calculation process executing on it. However, whatever unit price you set via that hook may be overridden by Rules that you weren't intending to apply to those line items. In my opinion, the best thing to do would be to write a custom Rules action to encapsulate your pricing and call it in a sell price calculation rule.