Reference price is a default custom field in Sellery set to the type 'money'.
This value can be used as you see fit. Some of our successful Sellery users use this value to account for MAP or a certain upper or lower limit, static prices, or, sometimes, just an in-house value they'd like to track for various reasons.
To tag your items with a reference price, you'll want to upload a file (Settings > Uploads) containing two columns: SKU and Reference Price. Populate each column with the appropriate SKU and Reference Price value for that item.
After you've tagged this value for any desired item, you can then reference that value in your Pricing Rules or create a smart list view that targets that field or particular values in that field.