While "price fixing" may be illegal, there is no law that prohibits a manufacturer from entering into legal binding contracts with retailers/dealers that dictate the selling price of a product and that those prices are subject to change based on Manufacturer promotions and negotiated sales.
To answer your question, you will not likely find an XT1 mower cheaper at one store than another unless that store is offering a special sale that they have been allowed to have. When Cub Cadet advertises their national promotions, the prices will usually change everywhere the affected models are sold. Profit margins are small on less expensive mowers, so if negotiations can be had, there is likely little wiggle room. I don't see many people haggling on price of a sub $3k mower.