The obvious big cost is the sheet foam, in it's different forms.

I spray foam the cracks of the last layer and apply a stick of strapping right at that moment, so spray foam is another cost.

Next would be the screws, I am using panel screws through the strapping and next into the timber and the planks(that is what I am using), I am guessing if you studded a light wall you could screw into the studs if you can find them?

Window bucket material, and the strapping is next on my list. One item the link shows them using is Ice and Water over all the exterior of the building, I have omitted this and don't factor it in as a cost.

I can see the use of it around windows after the buckets are set and before the windows go in and draining it to the outside by some method is also nice. This is a tight building and the windows will sweat. How about one of those air exchange systems, as part of the cost?

I am using clapboarding as the siding this allows the strapping to run vertically and on 2'centers. If shingles were to be used I think I would board on the 2' straps then apply the shingles, but that is a lot of extra work/cost.

Just some thoughts and input. Is that what you were looking for, Kevin? I think it is a nice system.

I also cut in the window opening after everything is attached on the exterior, for the most part. I adjust any of the strapping if needed. I save the extra foam from the opening and work it into the last wall on the house, as a first layer, resawing on the table saw if needed. So little or no waste, there is always some, if you were creative there would be 0 waste, for those greenies.