Your pricing sounds ambitious considering something like Autocad, which is a primary tool, costs about $2000/year, and you plan to charge $3000/month? Since this is essentially a cost-saving thing, I don't think it's realistic to try to charge the cost saved. If I as a customer can save $100/day by using your software, but your software costs $100/day, why bother?
Good point – it should be phrased as improved productivity. You have to think more broadly. You are not only saving engineer time. By delivering more in a shorter amount of time, you have compounding effects across the entire organization.
Eg, If I sell an animal feed supplement that increases cow weight by 1%, it means customers can increase output by 1%. If the same supplement can make racehorses 1% faster, that's something entirely different.