An "Offer" function on collectible items

This idea actually stems from a wacko dream I had the other night. Don’t ask me why. I’m not sure.

Users should be able to make R$/item offers on collectible items in the catalog.
On the drop-down menu on collectible items, add an “Offer” option. This would open a dialog box allowing for a R$ offer, and an “add items” button (which would open your inventory, much like a trade window).
Once you add the R$/items, the Offer box would show the total value (RAP + R$) of your offer.
You submit the offer and it gets added to an offer list on the item page.

The Offer page would be an additional tab next to Sellers and Comments. Offers should be able to be sorted by Value, most R$, or items-only.
Any owners of the item would be able to accept an offer at any time (think of them like trade requests, but for the general public to see/accept - not just to specific users).

Offers remain active until taken down by the user or accepted by an item owner.
Obviously, there should be an “Open offers” tab somewhere for users to see the offers they have out there and keep track of them. If an item drops way down in price, I don’t want to throw R$/items away because I forgot about my active offer.

Suggestion for this page: Show the item RAP compared to your offer value. If RAP is higher than your offer, your offer should be in green text. If RAP is below, your offer should be in red text. Just for easy aggregation of your offer (because in many cases, item value > RAP. So don’t remove them once they drop below - unless the user would choose that?).

When a user makes an offer, the R$/Items they offered remain in their account. They can make multiple offers on the same item, and offers on other items.
But as soon as their R$ drop below their offered amount and/or their items are traded/sold that they offered with, their offer should expire (they should be notified of this so that they can make a new one if they wish).
This would prevent users from offering a ton of R$ for one item and then getting rid of 2 or 3 of those R$ so that they can say “No see this item is worth X amount because there’s a crazy high offer for it” when that offer is actually false.

IF THIS LAST BIT IS NOT POSSIBLE, I don’t have a solution for the false offers yet. Open to ideas.

Post ant comments or suggestions. My train of thought was slightly messy when writing this post, so it may have been hard to understand. If you have any questions about it or if something was unclear, post below and I’ll try to fix it.
EDIT: I’ll try to make some mock-up pics of what I’m envisioning when I get a chance.

This is a good idea. I want this.

If you buy anything, sell anything or trade anything, all corresponding offers should be reevaluated and canceled if they become invalid.

This is still a good idea. I still want this.

I like this idea I was also going to say that steam has something some-what similar like this with buy/sell orders

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You can put however much you want to pay for the item and place an order, if it finds you a match it will instantly buy it. If not, it will wait for one to be for sell at your desired price.

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