DHL insured shipping – is the retail price or your own selling price more important?

For context: https://www.dhl.de/de/privatkunden/pakete-versenden/online-frankieren.html?type=ShipmentEditorProductSelection

Let's assume I received a TV as a gift with a list price/retail price of €550. The person who gave me the TV also bought it for exactly that price, and the warranty receipt also shows that price.

Since I don't need the TV, I want to sell it new and unopened on eBay for a lower price of €450. But what price is important for the liability of insured shipping? Is my own selling price the deciding factor, for which the standard liability applies up to €500, or is the general retail price or the invoice price from the purchased market more important, which is why I have to add the additional insurance up to €2,500 for €6?