Definite rip off.
Crescent Suzuki charged me £354 for the 14.5k service in Nov 2011, no valves needed adjustment.
I had the 28.5k service done at an independent garage in July 2012. The cost was £367 but that included the supply and fit of a Road Attack 2 front tyre, and the adjustment of two of the valves.
I had the 42.5k service done at an independent garage in January. The cost was £282 but this included the fitting of a light bracket and some bullet lights, and none of the valves needed adjusting this time.
The job does take longer if valves need adjusting, particularly, I think, if it is the valves on the rear cylinder as they are more tricky to sort.