What should the selling price of a 14x48 digital billboard be?

I just build a 14x48 digital billboard, it cost me approximately $480k to put up.
If the billboard is fully rented out in my market area, it can gross about $375,000 per year. I’ve been approach by different companies that would like to purchase the board from me, and they are asking me what I would like for it.
I am looking to sell it, but I don’t know where to even begin with the asking price. How can I quickly determine the approx. value in order to have a conversation with potential buyer? Thank for your help.

Don’t give them a price. Tell them, I’ve got several companies wanting to buy it, what would you give me for it? Make them make the first offer. Tell them you’ll sell to the high bidder. Once they give you their first price, tell them that you have a better offer, would they want to up their offer. Repeat the process until you have the highest offer, and that’s your winner.