If you're running a 2.3.0 server you're most likely dealing with the problem of "Item Not Found" when your players try to purchase some of their tier tokens or items. Just execute this one line code into your database.
Code:
UPDATE `items` SET `ItemExtendedCost` = '0';
What It Does:
It simply sets the cost in the ItemExtendedCost collum to 0 making it so that there is no longer a need to have the class tier tokens to purchase the items. However, keep in mind that this sets the ItemExtendedCost to 0 in your entire database and not just the tier items. It does not fix the core/dbc problem, but is merely a quick way around the issue. If you don't want to do this just wait it out or fix the dbc files or core yourself.
If you want to do what I did and just remove the buy price from all items in the game just execute this line instead. Again, this removes/sets the buy price for every item in the game to 0.
Code:
UPDATE `items` SET `ItemExtendedCost` = '0', `BuyPrice` = '0';
Cheers