OK, this is so wrong I need to show it so that those who don't know better won't be misguided by reading this:
the average income from arena attendance in my league is around 240k. mine will be 180k after my last expansion.
That's nice, that means the average income is around 244k without yours bringing it down. That's an extra 64k/week in profit -
on average - your rivals are banking. Now consider that the teams that are above average are getting even more than that. Yeah.
Dollars per seat is a useless statistic in a long-term game such as this, because there is no maintenance fee for upkeep of the seats. Every extra seat sold is
profit.
i can make 240k expanding to 7000/1000/150/0, which is a 8150 arena, why on earth should i bury millions of hard earned cash to expand my arena to 20k or similar and make the same money as a 8k arena?
This is plain wrong. Don't believe me? Go check out the Arena for the #1 team from your Blue conference in your division. He's spent the money to build a 14k arena, but made the stupid decision to set his ticket prices to max. Guess how much money he made last home game? 218k. And that's with a way bigger arena than your proposed 8k, and with his team winning more games than you. Fortunately for him, he seems to have realised his mistake, and lowered his ticket prices. Not by enough, but it should be an improvement anyway.
You're selling about all you can sell with your ticket prices maxed out. Each extra seat you add won't sell after a point, and yes your profit will be maximised. Until you learn to set adequate seat prices, you will never maximise your profit, and never reach your team's full potential.
To be the best, you must beat the best. Rather than comparing yourself to the average (and still finding that you fall short!), why don't we compare against some of the better teams from your league:
São Paulo Seekers made 287k in ticket sales last game, from a reasonable 14k arena (that guy should put some more LT in though, quick! And fix his prices, and his income will greatly increase).
Moikanos made 170k last home game in bleacher sales
alone. So his bleachers is almost as good as your whole arena.
And even Mr. 32k arena - he made a whopping 348k last home game!
You're giving up anything from 107k-168k to two other teams in your league - per
week - that they can then spend on better players and bigger salaries. Your weekly budget won't add up to a decent team unless you can first afford to pay for these players by selling seats.
To anyone still listening, take the advice of nearly every manager who bothers to read these forums and offer it - and invest in your arena. It will pay off big dividends in the long run - its why my team averages around 370k in gate receipts, and why I'm one of the most successful D2 teams in a decent country such as Australia (still aiming to make it to the top!)