Two neighbors both “installed a gas fireplace” and paid amounts that differ by a factor of four, and both paid fairly. The spread lives in four separable costs; here’s each one and its range logic.
Cost 1: the appliance
Entry-level builder units to luxury linear showpieces span several fold before anything gets installed. What moves it: size, heat output and efficiency, flame aesthetics (burner design, media options, glass panels), and controls (millivolt basics to app-connected everything). The appliance is where you set the tier; everything else follows the house.
Cost 2: the venting run, the swing factor
Direct-vent through the wall directly behind the unit: the easy case. Up an interior wall, through a second floor, terminating at the roof: real labor, materials per foot, and roof penetration work. Venting is why identical appliances install for very different totals, and why serious quotes come after someone has seen your wall, the no-chimney options guide maps the paths.
Cost 3: the gas side
Line distance from your meter, sizing (a big unit plus existing appliances can outgrow the current pipe), and pressure testing. Homes with gas nearby sail; homes where the meter’s across the slab pay for trenching or attic routing. This line also carries permit and inspection costs, non-optional and worth every dollar.
Cost 4: the finish
Surround, hearth, mantel, tile or stone, the frame around the flame, and routinely the largest single line on ambitious projects. It’s also the most compressible: a clean drywall-and-paint finish now, the stone upgrade during a future remodel, is a legitimate sequencing play.