Okay Folks, just found this board and registered... And as chance would have it, I just renewed my passport last week at Düsseldorf, so I thought I'd just add my tuppence, or 2 Eurocents, whichever...
The cost is €88, but if they send it to you, you have to pay €5 registered post on top -- makes €93 all together.. :$ German passports are cheaper, but they take min 4 weeks to get, and you have to go to the "Amt" twice - once to apply, once to collect. If you consider the time advantage, and the faster delivery, the consulate price is not so bad... The consulate normally takes 3 days plus postage time, so you normally have it within 5 working days.
If you need it faster, go there, they are quite freindly. Although they said they couldn't do it same day -- I did get there unannounced at lunch time -- but it could be ready the next morning and go out with the post. It actually arrived the next day, so either the post was unusually quick, or they did manage it same day after all

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You just have to be pleasant

If you really want it same day in your hand, then phone them before you go there and get them to agree to that, although you might need 2 days to get past the info system

Maybe that's just my accent, though
Funny thing the post... If you are at home, they don't ask for ID -- you just have to sign, although you could be a workman, or a burgler... If you are officially resident here, your driver's licence or your "Aufenthaltserlaubnis" are also sufficient ID at the post office -- mine each have different photos and different signatures, but are always cursorally accepted -- telling them it's in the bag is funnier, though ...