I'm almost even. I invested 1.2 mio in the arena and have already earned 1 mio. with the ticket sales. Currently I'm not sure what to build next. My biggest concern is that I'm under the salary floor and the 16 weeks are almost over. So before building some new seats I have to buy 1-2 new players. 
I'm in mostly the same situation, except I held off on investing an extra week or so recently because I had already overbuilt my current pricing, so my total investment is now 1.176M. Luckily I'm still over the salary floor, and thanks to an unexpected rivalry/TV win on the road the other day, I may pull in even more than expected. The goal is just to keep making the playoffs, keep building non-bleachers, and then see how things go.