Take the ebay price from the product discount field
Instead of entering a new price when listing an item from opencart to eBay, allow a discounted price to be used (standard opencart behaviour). This could be assigned to a customer group named 'eBay' and wouldn't be visible to regular customers.
This would mean that ebay prices are stored in the database and re-listing would be simplified.
Please don't. Solve this buy making price the ebay price and then crate a discount and assign it to the store customer group.
have done this way for 5 years