Cost varies based on what events you want to watch and if attending involves travel. Greensboro is about an hour away, so I didn't have to get a hotel room. I have a lot going on at home, work and the rink right now, so being at the event every day for a week or two wasn't an option.
If you want to see a lot of events, they offer package ticket deals for all events or just the Championship weekend events. if you have the time and interest to use a package, that's the best deal. Put your email on their mailing list as soon as the event site goes live and they'll let you know when pre-sales start. That's the best price for packages, but you're laying out the money well in advance, in some cases over a year earlier.
Here's the ticket brochure for NC2015
http://www.northcarolina2015.com/Portals/0/Ticket_%20Brochure.pdfI knew I wanted to see Sr. Ladies, the Gala Exhibition and Opening Ceremonies. A friend's dd was skating in one of the lower-level events, so I added that to my list at the last minute.
The Juv event was $10, which I bought it at the box office that morning.
DH gave me the Sr. Ladies LP tickets for Christmas. Our seats were in the lower level and cost $60 each.
I was someone's guest for the Ladies Short and the seats were prime so they were pricey - probably $85 each.
I bought the Gala tickets from one of my skating families who had a package but couldn't keep their little ones out on a school night. They were $30 each for seats in the top tier of the arena. I might sneak down tonight. Shhhh! (Spot the NY'er)
The only event in my list that the Champ Weekend package covered was last night's Sr Ladies LP and the Gala. The package wasn't worth the cost because I would have wasted/resold a lot of the event tickets.
Parking is an additional expense. The daily costs ranged from $7 to $15, depending on the event.
There have been empty seats (albeit in the upper deck) at every Nationals I've attended or watched on TV. I think the gala exhibition sells out occasionally but even today there are tickets available for tonight. So don't feel pressured to buy a package that has tickets you won't use. Another source is the Facebook pages of the local skating clubs or skating fan sites. People will offer to sell tickets at face value if they find they have a conflict at the last minute.