There are two prominent examples of antitrust/monopoly problems in the U.S. real estate market: MLS and dual agency. The MLS seems to be complicit in forcing home sellers into paying higher buyer agent commissions: https://therealdeal.com/national/2019/05/22/doj-demands-core...

With consolidation of real estate brokerage firms, many home buyers may have overpaid due to a single firm representing both home seller and buyer, known as dual agency: https://therealdeal.com/2019/05/01/houlihan-lawrence-fails-t...

There is a third issue of large private equity firms buying large volumes of houses that may, in the future, warrant an antitrust investigation.