IMHO, you may want to consider 4" square w/side brackets for ease of access with mud rings, as opposed to a 3-1/2" deep device box. It's faster to get in to bond, and a little wider on the sides. Easier to work with IMO, but either way, the $$ is much more than plastic boxes.
Include $$ for bonding the boxes. Green screws, pigtails, etc.
What reasoning did the HO give for metal boxes?? He may change his mind seeing the price.
Metal boxes? That's what I use! Both for customer service calls, as well as for rewiring my own house.
"Bracket boxes" dominate - standard depth 4-S boxes with the appropriate mud rings.
Correction: I use mud rings a bit deeper than I need, and set the boxes back to compensate. You'll want to make a spacer to help you set the boxes to the right depth. This practice means the drywall guy won't be fighting the screws on the face of the box, and things won't get beat up nearly as much.
Checklist: Boxes. Bracket boxes come in cases of 25. . Mud rings . Green screws w/ pigtails . Cable clamps (boxes of 100) . Mounting screws (short drywall screws are fine)
For dryer and range receptacles you'll want to use the larger 4-11 boxes, deep style. You can use a separate bracket to mount these.
The ho apparently enjoys building houses. He has a few 5k-7k houses around the country that he has built. He built one in Virginia that has 5 full masonry chimneys. He didn't like it so he built another and sold that one. He is very involved in the building process. He wants all metal boxes, copper plumbing, etc.
This is certainly a step up for me. I usually do smaller houses, remodels, service work.
I guess this is just a testament about how effective Carlon's marketing was. I am old enough to remember when electricians were fighting plastic boxes, swearing they would never use them. Florida pretty much makes at least a few of them mandatory if you are framing with steel studs. (another popular thing here) You are required to bond steel studs and the easiest way to do it is with a metal box or a plastic box with a bonded metal mounting tab.