I think it would be much better to have a small statisitic on the page sometehing like "successfull classifields last month".
If someone want to see allready sold classfields, then you sould add a filter for only showing this sold things.
just an example: You are going to a local garage sale and you found a very very nice thing (whatever), you really need and like it the price is also very nice. You like to buy it, but then you recognized the small tag on it - its sold :-(
Then you are going to the next garage sale, you will find the same thing, better price, but its also just sold. After that you will hit the roof? Right?
Keep in mind your users are looking for something, they want to spend money, and they dont want to see what is not available right now.
Its also success if there are no classifields on your page, because all of them are allready sold ;-)