Level up the maximum building immediately to 50!
Doing so you reopen the game for different "spendings".... and revitalize the game.

Ehm... change something in finance building.. talking about level 26 to 27.. why must you spend 190ML to get 265K/day ... to earn what you spent you need 717 days!

There is no doubt that the ROI for levelling the Finance building from L26 to L27 seems to make no sense but here’s another way to think about it.
It is not unreasonable to presume that players with L26 buildings will be clearing an average of 40 mil per day, possibly considerably more. After you have purchased all the Sport shop items that you want, building upgrades are about the only thing left to spend your money on. On this basis, 5 days after you upgrade your Finance building, your banks will have recovered the investment and you will be clearing 40 mil per day, plus another 265k.

What about new building levels? another idea can be: if you reached all maximum level structure you can reach the new level.
So, if you reach all structured at level 27 you can start with 28, if you reach all at 28 you can start 29.. and so on