Reply To: Product price on order detail and email receipt

[Soft79]

This is generated by the following function call in woocommerce/templates/emails/email-order-items.php:

$order->get_formatted_line_subtotal( $item );

get_formatted_line_subtotal calls the following filter: (woocommerce/includes/abstracts/abstract-wc-order.php)

apply_filters( 'woocommerce_order_formatted_line_subtotal', $subtotal, $item, $this )

Long story short: Use the filter woocommerce_order_formatted_line_subtotal .