Making the seating cheaper would only favour the promote at all cost teams who buy old geriatrics.
It would favour all new managers who have to build their arenas really. I don't particularly care about Utopia, they could leave the prices as they are over there.
More to the point, it would favor those who haven't invested in their arena, to the detriment of those who already did invest. So, say, two teams start at the same time, one spends on players and moves up, the other builds his arena. You now hand a huge advantage to the first team, who made the decision to win rather than build, and put the second team further behind the curve because they had the foresight to build a solid foundation for their team.
I'm not saying, incidentally, that the economy is perfect. I just hate to think that the solution to the problem is one that rewards the grasshopper for partying all summer, while the ant who gathered food for the winter gets nothing.