Flip Tax

Wow if true, that's pretty shocking. The 'fee' should at least be commensurate with shares held.

That is outrageous - check the Proprietary Lease to see if Transfer Fee is covered in there. Typical coops would have this provision and make clear this is something board cannot change without consent of specified percentage of shareholders. Is there nobody in this building of 115 units with desire, energy and skillset to take the board on? If the majority of shareholders don't want this, the board is ripe for a coup.

"This fee is great for large units and long time owners"

Just for long time owners. Id say instead , "Bad for all sellers, exponentially worse for small units."
Even the larger units in the million dollar range make this an effective 4% flip tax well outside the norm

Id be "coup"ing right along MCR but it doesnt seem to be a deterrence averaging between 10 to 15 sales per year.

If the tax was there when you purchased, then you benefited from the lower valuations it caused (not to mention subsidized maintenance along the way). Not much moral high ground to complain.

Co-Ops could/should have Flip Taxes , but shareholders usually vote down the measure in Annual meetings