Depends what you do. If you order a complete set from GW, it's going to be the most expensive. You could find a local marine canvas/upolstry shop. I find anyone like this will use good materials but likely not exact as stock (GW embossed logo for instance). You could do it yourself. You need SS or monel staples. You likely could use the same backer and foam if in decent shape, just remove the covers and recover using the removed as a template. For most of the pieces you just cut the material and staple, There are a few that need to be sewn. Just find the right thread for marine use and find someone to do these or supply the material (so it is the same as the ones you do) and have a local shop do it for you.
Local upholstery shop did my 282 Sailfish this fall, bolsters, both Captains chairs, transom seating unit and cockpit seats on live well and storage box. He used the same material with the bead as OEM....without the GW logo. Close to $2500 complete