Sure Tchibo is cheaper if you go online for more than 8 days per month, but Fonic is cheaper if you use data for 7 days or less. Nevertheless some people may prefer Fonic even when used for more than 8 days due to the more widespread availability through retailers, the low voice and SMS rates (especially the international ones) and the fact you need to maintain only one SIM during your stay in Germany and so less unused credit is likely to remain after leaving Germany.
As of the registration procedure, I amended step 5. Btw anyone can edit that page, as all the others on the
"prepaid wireless internet access wiki".