Market based pricing : based on the values in our area, I think we can set the price and fill enough of our units to make a profit.
Collusion : between the 14 of us, we own most of the homes in an area, I can safely jack up the price 200 bucks a month while cutting services and maintenance because we have a gentleman's agreement to keep the prices level. This way we all make money, it's a win-win? What are these people with no safety nets and exploitative employment gonna do, go homeless?
That's even pushing it. there's the common understanding of collusion, which this could maybe fall under, but doesn't matter legally. And then there's the legal definition of collusion which they aren't being accused of. The article doesn't say what law they are violating, or even if the suit is claiming they are.
Is it collusion for employees to coordinate their negotiations? Last I checked that was called "a union" and was a protected labor right. Businesses coordinating in a similar fashion isn't though.
Hiring marketing consultants to help you figure out how best to sell your product is perfectly legal. This lawsuit isn't even claiming a violation of any laws.
It doesn't even say but I assume this is a civil suit? you can sue for any reason you can think of in civil court. It doesn't mean you are correct. If this is a criminal suit then you have to tell the court what law was broken.