What you fail to realize is that
1) Record companies, don't, or at least shouldn't have a piece of that.
2) Concert prices go up to cover increased costs of liability insurance, gasoline, etc. While the average NET to the artist is going down.
3) You're talking about the top of the pile. That is not the industry. For all but those 10 -12 artists on top, plus the legacy artists.. touring goes more like this.. If you're on the road with a big artist, odds are your record company either paid for your slot to help promote the album, or your entire band is making less than $500 a night. You hope and pray that enough of the people who weren't there to see you decide to buy a T Shirt so that you can eat that night, and drive to the next city in your busted up van. You've got crew and musicians that HAVE to be paid, and there is a very probably chance that by the end of the tour, you as the artist have actually lost money. If you're headlining a small club tour, its a bit better but not much. You're grossing maybe $5,000 a night, still have to pay musicians, crew, gas, hotels, keep the van or bus in good shape, Liability Insurance, equipment, etc. Your Agent is taking 15% of that, and your manager is probably taking another 20%.
If you can make a living (30-40K) doing your own music for a year, thats a major, major victory. Just try and gas up a 10 cylinder van and drive it 400 miles to the next show towing a trailer at $4 a gallon.
The blame for concert ticket prices lie clearly on Clear Channel / Live Nation and our government that allowed them to become a near unstoppable monopoly, and it also falls on the shoulders of sue happy lawyers who file constant nuisance lawsuits because someone went to a concert and got hurt in a mosh pit, or lost their hearing standing next to the speaker.
A major legacy act might make $30K a night, but they're supporting 30+ People on the road and still have to cover all those expenses.