Used to be in the business. Around here this is the slow time of year. There are several reasons why they are having a sale of new units. They could have been pre-purchased with a deposit by a builder that due to the current housing market now is not building houses. So the local distributer is stuck with certain models and needs to move them out ASAP. Some HVAC contractors will pre-purchase on spec x number of models for the upcoming season. Something happens and that contractor can no longer honor his agreement. Again the distributer will offer these units to other contractors at a bargain so they can unload them.
Pre-purchasing in the off season is a common practice in some parts of the company. And sometimes the deal goes bust.
But again as always it is buyer beware. Check out everything before signing a contract. Tell them you need 72 hours to look it over.