I suggest you consider structural insulated panels (SIPs) and Huber's Zip-R sheathing as alternatives to ICF construction. I like either better than ICFs irrespective of cost.

Thank you but cost is my primary problem at the moment.

Either option I suggested will be a high performance, lower-cost alternative to ICFs depending on the particulars of your home design (SIPs don't lend themselves to home designs with lots of zigs and zags.)

2" x 6" stick frame construction with spray foam insulation in the stud cavities isn't cheap. Huber offers Zip-R sheathing with a variety of rigid foam thicknesses--all of which will eliminate the thermal bridging of wood studs. You may be able to achieve the desired R-value and have a better performing wall assembly without going to 2" x 6" construction.

Discuss all of the available options with your architect and your builder.

If costs are that big of a concern, then you cannot afford to build. The cost difference % are almost insignificant in the face of the overall building costs.

Not a huge concern. Looking for ideas to trim about 15% of cost. This question was one idea. With lumber prices falling to under $600/lin ft and the rising costs of ICF blocks, rebar, concrete, pump trucks, etc, it seemed a logical place to probe. The historical standard was ICF was ~10% premium, which would payback over the long term in reduced energy savings. I was just asking for SWAGs on my specific question from more knowledgeable people than me, based on today's current financial situation with falling lumber and rising inflation. I wasn't looking for other suggestions or opinions.

Value engineering is done one line item at a time with knowledgeable folks directing the process. Pre-covid, we found that savings produced by value engineering topped out at around 7% of total construction costs without making major changes to the home's design. A 15% reduction is a big number. I suspect you'll need some amount of redesign vs. component substitutions to achieve that.

15% is a reduction of space by about 30%, and a reduction in complexity too.

Re your several mentions of the acronym ”SWAG”. That acronym has a number of meanings used more prevalently than how you meant it. The acronym may be offensive to some, humorous to others, or an eye roll to others. Perhaps you’d be better served with the more straightforward words ”estimate” or ”guess”. Or just keep using the acronym. Giving you a heads up is all.

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This remnant of the silent generation thanks you for the tip!

(I'm keeping my opinions to myself.)