There is no current official trading value system, as highlighted in our official value list article. We do not endorse other value sites as while these are useful tools to the community, we cannot guarantee their legitimacy and they could be falsifying values in their favor. They do not have inside knowledge that contributes to the true value of an item, such as how frequently an item is traded or the scarcity of an item, and so may not be reliable.
If a trade isn't fair, a warning will let you know. This warning works off of the number of items placed in the trade, and the difference in rarities. If this warning appears, you should reconsider or decline the trade.
You can join our Discord server with a dedicated Win, Fair, Lose channel where experienced community members can react to each message to tell you whether you should continue the trade. Alongside this, it is always best to use your intuition.
To join our Discord server you must be over the age of 13 as per Discord's Terms of Service.