As someone who's formerly worked in entertainment production at a fairly high level...

-Tickets have always been "expensive". For instance, the average cost of big name arena act tickets in the mid to late 1980's was around $15-$20 which is something like $50-$60 in 2016 dollars. The band will obviously charge what the market will bare... but the manner in which show tours are done hasn't changed that significantly in the past few decades... so it's not surprising that ticket values have held at the same approximate pricing where bands can tour, pay everyone to make it all happen and can make a profit at a price that patrons are willing to pay to see them perform.

-Everyone takes a cut. Ticketmaster is just one small part of a big food chain but it's the most public one. Money flies all over the place to put on a show and deals get granular all the way down to things like the band possibly having to rent space in the venue to sell their merch or maybe a union town requires the venue to sell it for them at a fee. Maybe there's a cut in bar and concessions going back to the band. There's security costs which may be covered by the venue fee or not depending on the act's rep for trouble. Maybe the venue has more pull to draw people in than the band or vice versa. The people in this biz are experienced in determining value and making deals based on revenue expectations and while there's some average numbers... there's no standard pricing written in stone for these things. It just all goes out the window when someone like Led Zep decides to do a reunion tour or some new act drops a hit single where the biz folks will negotiate tougher than the fukin' UN for their cut. If you doubt this then remember that Sony tried to kick Tarantino's Hateful Eight out of ArcLight cinemas to show Star Wars instead over the past holiday.

-All things considered, a 30% markup is a pretty common minimum desired profit benchmark for many businesses that are trying to sell you something. Of course, businesses don't normally tell you what they're making off the thing they're selling you so Ticketmaster is very unique and vulnerable to criticism here because they have to disclose this info. Companies like Apple don't take nearly as much of this type of flack when they release a new phone, someone tears it down to give people a production cost estimate, it's discovered that Apple makes much more than 30% on every phone they sell, everyone knows that they have billions in the bank because of this... but they still buy and love their phones. Finally, it's very possible that Ticketmaster gets different profit cuts based on individual deals they have with the acts and their business model just makes more sense to charge a standard rate the market will (begrudgingly) bare. Maybe one of their selling points is that they play the bad guy in these deals instead of the bands trying to charge more than what people would normally pay to see them. Gawd knows what deals are being made behind closed doors between the acts and Ticketmaster but I highly doubt it's as simple as it appears.

-As for the venue fee, the venue has to make money and someone has to pay for it. A common way is that a promoter will book the band, sell the tickets, collect at the door and pay the venue their fee out of ticket sales. Didn't sell enough tickets? Tough shit... the venue still wants its money. In this case, they're using Ticketmaster to sell the tickets and both are passing on the venue fee to the punters for a small cut from Ticketmaster to handle the transaction. This used to be included in the ticket price so maybe they have to legally break out that cost for some reason now. Yeah, everyone hates tacked on fees but they offer a good service as far as the acts are concerned. Once Ticketmaster established itself as a universally known ticket source, they were able to reach a much larger market of ticket buyers as opposed to these acts trying to sell tickets on their own. On the buyer side, you have the convenience of buying tickets online or in established easy to access locations as opposed to trying to find the band's website or standing outside the venue in the cold to buy them. So the cost is unfortunately a necessary evil for your convenience and the acts doing business.