lol...That used to be the rule of thumb for a big Class A diesel pusher. The Sprinter is more akin to a passenger car/van/SUV.
There are thousands being used exactly as you want to use them. Other owners will chime in here on the costs. While the service may cost more, the intervals are longer and you get better fuel economy. At the end of the day, in a small unit like this, I think it all washes out. We'll have our gas E450 out next month, but I still like driving the Sprinter better.
PLEASE do not send questions via Private Message, my inbox fills up too quickly. Post questions in the forum as a new thread so that other users can benefit from the answers. Use Private Messages for sensitive information only (VIN, Contact info or things you do not want the public to see).