Creating an item that can only be purchased once?

I've searched all over, and this seems like such an easy-to-accomplish task, but I can't figure it out. I want to create an item that, once purchased from a shop, can never be purchased again — is removed from the shop, never to return.

How can I do this? I know it must be easy, please know that I've spent time trying to figure it out myself and Googling it.

Neutral Buildings - Add item to shop

Something like that anyway, at map initialisation. Then, when someone buys it:

Neutral Buildings - Remove item from shop

That was the first thing I tried — but it didn't work. I'll play around with it some more. Thanks for responding so quickly.

The shop in question does have "Sell Items" as an ability.

The "remove item" action can only be used on items that are also added via trigger, as Griffen implied.

Thank the both of you for your help. I did pick up on the implication of Griffen's, and that works fine. However, my item has a techtree requirement I'd like resepected -- so I guess I might be out of luck without some tricky triggers, because as far as I can tell, when you add an item to a marketplace via triggers, it doesn't respect the techtree requirements.

Thank you both again!

Requirements will only work if it is like an Ancient of Wonder, or the other 3 player ones, not like the neutral market places. You could trigger the requirements, and return the money, if it is just a small number of them and you can't get to work like the player ones.

They are player shops, not neutral shops. The requirements work like a charm — but I want the item to only be purchased once. I'd really like this system to be as elegant as possible — which to me, means being unable to purchase the item, as opposed to purchasing the item and having an auto-refunding auto-destroying trigger. Damn.

On a someone related note, as long as I have your attention — sometimes when I add the item to the shop via trigger and purchase it, the item lands on the floor as opposed to inside my hero's inventory. Any idea what could be causing this? Thanks again.

Well, having a player shop and then using these triggers would probably work.

As for appearing on the floor, that's player shop specific, I think, and occurs when you don't have a hero with any inventory space available nearby. I think. It's late, so I can't be sure.

It was my dumb mistake why it would land on the floor — I didn't give my shop the Select Hero ability.

To handle the elegance issue, I made a dummy upgrade with the same appearance as the item I want to sell. When the requirement is met, I set the research level to 1, removing the upgrade, and then I add in the item. It all works well and looks well.

Thanks again for your help in this!