The runescape market is heavily focussed on the serious merchanter gaining several items that are no longer brought into the game. These items have previously been dropped by Jagex on holiday occasions and have since been discontinued.
Holiday events have taken over from holiday drops and as a result, the original items that were dropped are now rare as they will never be replaced. As time goes by, people may get banned, lose the rare item through their own fault if they accidently cast the high alchemy spell on it, or simply a player may have quit runescape for good.
As a result of all this activity, the price of these rare or discontinued items invariably increases over time.
With the exception of the Bunny Ears and the Scythe, all of the other items shown in the picture are highly sought after rare items. The Bunny Ears and the Sythe cannot be traded to other players and are therefore not able to be merchanted or sold.
The highest priced item on the list is the Christmas Cracker as it contains an unknown coloured party hat - it will be one of the other types that already exist, but is priced similarly to the highest priced party hat which is currently the Blue Party Hat.
Both the Pumpkin and the Easter Egg are items that can easily be eaten and therefore over time are rising in price - although currently they lag a long way behind the desire for people to own a Party Hat.
The Halloween Masks and the Santa Hat are currently very desired items and almost daily or weekly increase in price. Invariably, as the holiday season approaches for either item, the price will likely show a sharp increase and many merchanters will be seeking to take advantage of this scenario.
Owning a rare item brings its own problems - people may try and scam you out of the item or trick you into selling it for a much lower price. My advice is simple, always know the price of any item that you wish to sell and in the case of rare items, the price can fluctuate at different times although over the long term the general trend will be an upward spiral.
There are two other items that were not holiday drops, but moreso, are now discontinued items. These items are also rare because no more will be brought into the game - although they are now redundant items themselves, they still retain a trading quality for people looking to merchant them over time.
The disk of returning was previously used in RuneScape when normal players wished to visit this 'black hole' by purchasing this disk, and spinning it to return from the Black Hole. The 'black hole' was basically an area where players who had broken rules or cheated were held.
The half jug of wine is now discontinued due to a change in the Cooking skill. In the past, Wine was changed so it took 1 swig, not 2, and only people with half jugs at the time of the change will have had these. Consequently, most players sold the half jugs of wine as prices have increased over time.