Here's a little comparison between prepaid tariffs in Germany back in 1998 compared to 2010. The comparison isn't quite easy as there are so many different tariffs and operators today that you can easily come up with something cheaper but with different strings attached. So this comparison just gives a general idea of how things have moved in a decade.
There we go, according to this (very old) article in a "Fokus" magazine back in 1998, prepaid prices in the D1 network were DM 1.99 (€ 1.00) during daytime and DM 0.99 (€ 0.50) after 8 p.m. In the same network today, service providers offer calls for € 0.09 a minute around the clock. In other words, it's 10 times cheaper today (compared to the former daytime tariff) than a decade ago and still 5 times cheaper when compared to the night time tariff.
Equally amazing is the initial price of the SIM card. Back in 1998, the SIM card cost DM 149.- (€ 75,-) with € 25.- of credit on it. And that didn't include the phone. Today, you get a SIM card and a very basic phone for € 10.- with some credit already preloaded. Again, a significant magnitude cheaper then a decade ago.
Yes, I know, 9 cents a minute is by no way the cheapest offer on the European playing field anymore. Austria, for example, has prepaid tariffs for 4 cents a minute (example can be found here).