1) The stadium was built with other purposes in mind - concerts, trade shows, etc. Remember, there are 8 football games played in that stadium a year + playoffs (lol) and a college bowl game. At most, that is 11 football games. That's hard to pay the bills with. So they designed it with extra space so it would be enticing for other events like SX, Monsterjam, trade shows, and concerts. It's a very cool stadium for sure.
2) Attendance was lower than I've seen in the last 10 years. The stadium holds about 60K and it might have been 65-70% full max. I'd guess about 35-40,000 people were there. Phoenix normally has about 50,000 people in attendance.
3) I don't think the lower attendance was due to price. You could get lower level tickets in the north end zone about 20 rows up for $35 plus the fee. That's a damn good deal. I don't know how much the cheap seats were. We were in the front row and our tickets were $65+fees. They were great seats. I'm not complaining about ticket pricing, that's for sure. I don't know why attendance was down to be honest.