In my locale, ICF usage has been adopted by home builders who have become fed up with the lousy jobs done by some (not all) of the poured wall foundation subcontractors. The lumberyards kind of got the ball rolling by taking on product lines and going out to try to sell some packages.
What I have seen is that as soon as one lumberyard started to sell ICFs, the others all followed. All our local guys now stock and sell the blocks and everything else needed to do ICF, and they "lend out" the entire package of bracing and scaffolding planks as part of the cost of doing biz.
I can get Arxx from one, and make some calls elsewhere and get Logix and Amvic. The price seems to have leveled to between $19 and $20 per block, that for the nominal size of 11 thick x 48 wide x 16 high. The 6" core block here is what is commonly used for foundations. Sales tax is added, but no freight. I've seen very little usage of ICF for anything other than foundations.
Your mileage may vary.