My machines never return to dealers except for safety recalls. Therefore, my 600 mile service probably cost me less than $25 for supplies. Note that the DCT has an extra oil filter not used on the manual transmission. Dealers have been known to be ignorant about the DCT filter. There’s very little that needs to be done at 600 miles so I can’t imagine it being a reason to take it to a dealer. It’s pretty much common sense inspection and adjustment that owners should really be doing themselves for their own safety.
By law in the U.S., warranties do not require you to pay a dealer for the service. Just keep records and receipts.
If you Google “nc700-forum 600 mile service”, there are a whole bunch of prior threads on the 600 mile service topic.