I followed Mageworx answer above and added price_per_unit attribute to the attribute set where it was removed. However I threw it in the main group and it didn't work. There's one additional component to this. It has to go inside the mageworx-dynamic-options group.

From the Mysql CLI, I did:

mysql> SELECT * FROM eav_attribute_group WHERE attribute_set_id = 4 AND attribute_group_code = 'mageworx-dynamic-options';
+--------------------+------------------+--------------------------+------------+------------+--------------------------+----------------+
| attribute_group_id | attribute_set_id | attribute_group_name | sort_order | default_id | attribute_group_code | tab_group_code |
+--------------------+------------------+--------------------------+------------+------------+--------------------------+----------------+
| 485 | 4 | Mageworx Dynamic Options | 16 | 0 | mageworx-dynamic-options | NULL |
+--------------------+------------------+--------------------------+------------+------------+--------------------------+----------------+
1 row in set (0.00 sec)

I just added another row to the table but with the attribute_set_id 73 which was missing.

mysql> INSERT INTO `eav_attribute_group` (`attribute_set_id`, `attribute_group_name`, `sort_order`, `default_id`, `attribute_group_code`) VALUES(73, 'Mageworx Dynamic Options', 16, 0, 'mageworx-dynamic-options');
Query OK, 1 row affected (0.01 sec)

Make sure you edit the attribute set where the attribute was missing and drag and drop price_per_unit into that group which should now be there.