That’s not collusion that’s just optimizing price for profit. You can have ‘collusion in effect’ with price matching on a market leader where multiple companies

That’s not collusion that’s just optimizing price for profit. You can have ‘collusion in effect’ with price matching on a market leader where multiple companies can price as if they were a single company monopoly without explicit coordination. There are many situations that are not considered true monopolies that I think should be, such a geographical monopolies that occur when there is a tacit agreement for companies not to enter each other’s areas of operations.