I actually think it's a good idea to take it in for the first servicing regardless of cost. More so if you've done any modifications.
I felt with a brand new bike it was important to me to have it 'on record' that the bike was in fine shape and that it was indeed serviced by a certified Triumph shop for the initial servicing.
My thinking is that if there is something really wrong with the bike that it will probably reveal itself before the second servicing. I didn't want any hassles resulting from not being able to show that it was serviced to manufacturer's specs. Not that Triumph would necessarily do that, I'm just paranoid like that.
I also used it as an opportunity to get the bike dyno'd. You may want to do this even if you haven't done any mods yet. That way you'll have a clean baseline to compare to later on.