How to determine good ticket prices for music festivals?

So for concert lovers, i so badly want to go to the Welcome to Rockville fest, each year they always have killer line ups. This year is insane and would be a shame to miss. Four 4 days for ONE person is 400 bucks and i find that absolutely outrageous, it’s reasonable to go one day, but theres no 2 day passes which annoys me. Because i don’t care about half of the bands on some of the line ups. Why force to pay for 4 days when you wont see all of them. I know its a festival and you get festival activities and such but like those who have gone is it worth it?Ive been to may concebit not a rock fest, im just questioning the safety n such of it all as well.