Here's my theory:
Venues and bands know that for PR reasons they can't jack up the price of tickets, but they don't want to miss out on the revenue from people willing to pay scalper prices. So they set tickets at a nominal price but reserve huge blocks of tickets for the band and venues. Nominally these are "family and friends" tickets, but in practice the band and venue put them immediately for resale. This way the bands and venues can get that gigantic revenue. Meanwhile a small number of tickets are sold at face value and immediately sell out. Ticketmaster profits from fees on the ticket sales and resales.
A "known evil" company like ticketmaster is now a benefit, as "obviously" the jacked up costs are ticketmaster's fault. Meanwhile ticketmaster is really just a service to take the heat off of bands and venues for what would otherwise be seen as price gauging.