Answer:
No, it violates antitrust laws
Explanation:
Antitrust law as applicable to Real Estate, is a law that is made to protect stakeholders: buyers, sellers or other parties involved in a potential or actual contract relationship from practices that may be considered as void such as price fixing (often times lowering of prices), rigging of bids, allocation of customers or markets, running of multiple listing services individually or collectively, and group boycotts.
Hence, in this case, this is a case of price-fixing where by two participants on the same side, have agreed to fix a price, in which the 5% may have imposed high prices on consumers. Thus, it is considered illegal, and violates antitrust law.