Yes Victor, it is expensive. I have a Snap On MTG 2500 and Mercedes cartridge. Ebay is a best source now. Here is one for example.
MB cartridge:
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=330087276384
And the scanner from the same guy:
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=330174183204
I remember paying about the same for the cartridge from Snap On and much more for the Scanner, but it had cartridge for Domestic cars.
Mike