As you might expect, the answer is "It depends." If your stove is close to an outside wall or doesn't have living space above it, costs might be lower. The factors will be
1)how can we get a pipe to the outside? Through a wall, or up through the roof?
2)do we have to reconfigure cabinets to install it?
3) how easy is it to connect wiring to install the fan?
4) can we do some or all of the labor ourselves?