How much should i sell this for, got offered 5 mirrors

Hey,

im pretty new to the game and still struggling from time to time to price an item. with this one, there is no item like that on the market and some chinese guy offered me first 80ex than 200ex, 300, 500 and at last 5 mirrors. I'm completely lost, also bc i think it's not even near worth that much?

/closed wrong forum...