Currently trying to print a large prototype myself and found some interesting services along the way:
Cheapest service I ever found is fabberhouse.de , with 0,49€ per cm³ Material.
Catch is, you have to get the Printer driver and convert, check and inspect the model yourself and they only have one white looking material. But the price is unmatched, since you do most of the work yourself ;]
You chose every last detail in the printer driver, so if you do the walls only grid filled, you will pay less.
Max. 25x25x30 cm
Too small for me.
Second cheapest with a good assortment of materials is a local service in dresden run by a printer manufacturer,
http://3d-druck-dresden.net/3d-druckservice/No premium post processing the big printing services do, it seems.
In my case 1900€
All other services seem to be in the same ballpark figure for the same material.
No matter what service, in range of 2500-2800€ in my case.