Anyone that give you a price without knowing the variables is misleading you!
You need to state: * How big is the house? * What kind of walls need to be ripped out to run duct work? * Age of house? * Type of house design? * Type of attic? * Climate (where you live)? * Etc. etc. etc.
Someone could recommend a heat pump in the attic to service the second floor, but depends on where you live & type of attic.
If you want "US" to give a reasonable response, then "YOU" need to spend some TIME and provide the necessary information.
Sorry if I sound critical. People keep giving me grief because I'm BLUNT and to the point.