Welcome!
First off. Which generation are you looking at getting? That's going to be a bit of a factor on parts availability.
I think you need to look around and see what kind of parts you actually want. Saying I want a touring windshield is like saying I want a can o pop/soda. Lots of different kinds, and different prices. DIY heated grips are just north of $30. But you could buy actual grips with heaters in it, or I've seen heaters that go into the handlebars themselves. Those are more expense I believe.
There are a few windscreen companies out there. Probably the popular three are Zero Gravity, Puig, and Givi. I've bought my ZG DB for around $60-$70. You're probably looking a few bills more than that for a touring screen.
Luggage racks vary as well. Looking for soft luggage, full GIVI bags, OEM hardbags, Pelicans? A set of hard luggage is probably going to be $400 and up. Soft luggage is easily had for any price. You have to look around and see what you want.
HIDs: Thought they were coming down to the $100 level. There was a thread not too long ago about HID conversions. Look it up in the forums.
Heli bars. I think they're $150 range. Someone else should give a better idea.
Pretty much you need to poke around and see what you like.