Tradeable items can be:
When RuneScape was first released, all items could be traded. However, following complaints that quests were too easy this way, many quest items were made non-tradeable. Member items are non-tradeable and cannot be high-alched on free servers.
When trading items with another player, players will be notified of the market value of the item, and the "wealth" that they are transferring to the other player. The old method of checking current prices of items, commonly called "Price check", was by trading with other players. To facilitate this, a feature known as Price Checker was introduced in 2009. This feature is accessed through the Worn Equipment menu.
All non-tradeable items and items worth more than 5,000 coins, when dropped, do not appear on the floor to other players. These items will disappear (to the player who dropped it) after a certain time has elapsed.
There is a trade limit for "wealth" that players can transfer to another player, and this increased as more quests are completed. See the trade limit article for more information.