We often assign a number to evaluate the value of things, but is everything measurable? Is the value of IT measurable? Paul Strassmann, the CIO guru, once argued that IT is just as basic as the accounting department, it is nearly impossible to attach dollar values to an IT investment. Yet, we still use ROI to evaluate an IT project because without a metric, it is hard to keep track of the performance, the success, the failure, and/or the impact of the investment. Such numbers and value attached allow us to compare in quantifiable measurement with respect to the set goal. IT investment is risky and often require large amount of investment. A successful project can have a long return on investment period; yet a failure can cause the company money and time. Even with a high probability success rate, the outcome is still 50-50. Thus, the value of IT is subjective. There is no real formula in calculating the value of IT, but what one thinks about the possible cost and benefit IT can bring.
https://www.cio.com/article/2438921/it-organization/everything-is-measurable.html
I agree that measuring IT can be an extreme challenge in the business, and I agree with the author of the article that it is mostly because IT investment cannot be analyzed in the same ways as other business units. I would put most of the blame for this problem on the leaders of the IT teams inside the business. I currently work at a financial services company where I help manage IT infrastructure for the firm, and one problem we run into is explaining how projects benefit the business and what are the metrics for success. If we measured our projects we would see a lot more adoptions of IT projects. This is anecdotal but the author mentions in his article that this problem is across the industry. So IT is measurable and not subjective, it just needs to be tailored to the specific projects IT teams handle.