Inflation...?

I went to the post office this morning:

-Could I have a 10-pack of 78-cent-stamps, please.
-Certainly. But a 78-cent-stamp costs actually 82 cents nowadays.

I have to say, I was kind of amazed of getting a 10-pack of 82-cent-stamps costing 8,20€ instead of a 10-pack of 78-cent-stamps costing those 8,20€...