Auction house is a bit unintuitive and won't allow you to search the market history unless there's a listing in there already. You could try posting for max (30b) and then click on it and search market to see if any have been sold recently. If it sells for 30b then hey, you came out with 30b.
My best guess is around 50m, but anything can be worth as much as someone is willing to pay for it. @gakinotsukai you can search anything in the market history, you just have to look within its search category (e.g. "Etc items" -> "Item type: Chair" -> "Item name: Olivia"