I am sorry to disappoint you but the AK47 £5 notes can go for as low as £7 on ebay.
If you go to advanced, then sold listings when you look it up on ebay you can see the actual amounts paid, rather than the crazy amounts people on there ask.
A completely selling policy is that the buyer is present or absent at very high rates. I do not think I keep the price level too high, I will sell it if the buyer comes out. If the buyer does not go out, I will keep the money in my collection, not trouble.