I think you are asking about a new furnace? If so, that might vary by where you live as to the cost of the unit, the labor to install it. You might look at some of the results linked here: www.google.com/?gws_rd=ssl#q=price+of+furnace+for+2000+sq+ft+home they might help give you some idea.
We just replaced ours a couple of weeks ago - Cost us $6150 for a natural gas/AC (80 AFUE/16 SEER unit). Ours is an outdoor package unit, so it's a little different than most of the typical split setups.