I've joined forces with the hobbyDB team to create a database of every Starbucks Mug ever made! You can use hobbyDB to manage your collection and wish list, show it off, find values for your mugs, and to trade, buy and sell. We currently have four volunteers and would love to have more join the team. If you'd like to help, contact the guys at hobbyDB.
Starbucks City Mugs 
Why are they discontinued? Especialy the Groningen?
They are the older series and this series has been discontinued for a while now.