Spec grade devices? Gonna be a fair chunk of cash. How many dimmers? We just did a house, less than 2k square feet, and every single light was controlled by a dimmer. Add in LED bulbs and those are ~$25 a pop. Fan control switches, 3-4 control bathroom fan (light, nightlight, heater, fan) switches?
Also, any house more than about 20 years old will have ungrounded switches and probably no pigtail in the box, so time to redo every single ground has to be considered. Double wired (two wires on one screw) and backstabbed #12 ga receptacles will have to be rewired completely. How many switched outlets? Did one of those 5500sq ft McMansions where every receptacle in the living, dining, family, office and bedrooms had switched receptacles. How many Bakelight/fiberglass boxes with blown/broken pieces that include a device screw hole?
Regular coverplates or wood/metal?
and if you are adding AFCI, simply inform the customer that they have to be T&M; it may just be materials, or you might spend half a day tracking down neutrals of different circuits that are tied together.
I think you could walk this house and get an accurate count in 90 minutes or so. Also, keep in mind that USOC keystones for telephone cannot be wired daisy chain; splices cannot be made on the device, so use regular 4/6 screw telephone wall plates, or plan on splice/pigtail all phone lines.
