MySQL database design
I'll take a crack at this.  Note, that I've just listed fields that are necessary.  If you have additional data you want to store for in those tables, feel free to add them (so long as they are normalized).

While you did state that you would use a different database for each region, I designed this so that they could all work in one database.  Right now you may have only 5 regions, but this offers the flexibility to easily add more:

table: region
regionID        varchar(2)
regionName      varchar(50)


Defines data for each realm.  I went with a surrogate key (realmID) because it's possible that realmName might not be unique.  This assumes that each realm can only belong to one region (regionID needs to be a foreign key to regionID on the region table):

table: realm
realmID         int
regionID        varchar(2)
realmName       varchar(50)


Defines data for each user (seller/buyer).  I decided that it would be better if it had a surrogate key (sellerID) because seller/buyers first/lastname combinations may not be totally unique.  Note, you may also want an address table to store multiple:

table: user
userID          int
userFirstName   varchar(20)
userLastName    varchar(20)
userEmail       varchar(100)


Data for each auction.  AuctionID would be a auto-generated ID and the Primary Key.  You would also want foreign keys on realmID (realmID on realm table) and sellerID (userID on user table):

table: auction
auctionID       int
realmID         int
sellerID        int
auctionPrice    decimal
auctionStart    datetime


Data for each auction that has been completed with a foreign key on buyerID (userID on user table):

table: auctionHistory
auctionID       int
buyerID         int
finalPrice      decimal
auctionFinished datetime


I don't think that you'd need a seperate table for "Scan".  That would be a simple query of rows in the auction table that do not have matching rows in the auctionHistory table.  Hopefully, this will help you get started.  If I missed/misread anything, please let me know.