The first team to win Utopia didn't have that much arena seats. He was basically investing money into veterans, won games, hence filled small(ish) arena with big prices.
Of course, he knew what he was doing. A not so skilled manager would not profit from such a tactic, and should build arena instead.
What I'm saying, let's say you have a hypothetical league. If 8 teams go arena, 8 teams go full force, 1 team will win a promotion, but other 7 teams will be in a weaker position than those 8 who prepared for the future.
Basically, if you want to be a tough guy, you better be the toughest guy, or you're screwed :)