Well if you wanna know how much did u spent on apps in the App Store now you have an App for that.
This onereally impressed me by the easy of install and use.
The App will just live on the Menu Bar and from there you can customize it a bit.
You can even edit the price of your apps for any price. And for this of course your are modifying the original price. But if want to impress your friends with a 1000€ spent go ahead!
Hope you like it!