Depending on the name brand and the SEER rating, prices differ from 1200 USD to 10,000 USD. The higher the SEER, the most energy efficient the unit will be. In the US the mimimum SEER rating is 13. Also to properly work the unit size, in tonage, has to be specific to your home size.
depending on what you want and the size of the house,roughly a total complete cetral heat and ac installation job for a three bedroom house with 1500 sq. feet duct work units copper electrical would be about $3500 to $5000
That would be dependent upon the size and brand of the unit which you purchase and if you are able to do a self install or have to hire someone to provide that services. Between $3000 to $5500