Look, it says in the manual, "fans will buy the most expensive seats they can afford". Or something like that. The point is, bleachers cannot suppress lower tiers.
You're free to build more lower tiers, those extra bleachers aren't hurting you. How much money have you wasted? 3k bleachers, which is 600k dollars. You pay that for one week of salaries!
In fact, lower tiers can suppress bleachers in some cases. And that is your case! You're selling 16k bleachers at maximum price of 20 dollars! Meaning, if you had less bleachers and more LT, sure you would gain some extra money on LT, but you would probably lose more on bleachers!
And don't get me started on how bleachers can be your bread and butter in lower leagues. Let's say you have 8k bleachers and 4k lower tiers at some lower league. Your bleacher tickets are at much bigger percentage of the maximum price, than your lower tiers. That means, you're going to return the money way sooner with upgrading your bleachers. Example, if you manage to sell your expanded seats at full price, you need 10 games to return the invested money. If you sell your expanded seats at 50% of the full price, you need 20 games to return the invested money.