The idea that lots of full body MRIs will necessarily lead to better discrimination of malignant vs benign anomalies assumes that the imaging is able to detect differences at all, which often is not true. Some benign and malignant abnormalities can look _exactly_ the same on imaging, particularly at an early stage, when you could make a difference, for example lung nodules. Nevermind the fact that many benign entities can undergo malignant transformation at some point in the future. Or that MRI is only a good test for a subset of cancers, CT is better for others. All these issues help explain why doctors are averse to full-body scanning everybody. It is neither cost-effective nor medically sensible.
I think their statement is more general than what you're making it out to be. The goal of receiving better and more data puts pressure to have better imaging technology.
I think there are perverse incentives at work, too. If running the MRI machine cost $100, people would do it. If it can bill insurance $100k, and then any follow up might cost $500k, there is a rational aversion to doing it as it might make the _system_ less good for everyone if insurance cracked down on exploratory imaging as a billable thing (obviously, they already do this to some extent).
Better technology is unlikely to be cheaper, unless it is so new and novel that it can get its own unique billing codes, and if it becomes ubiquitous so it cheaper and more available than existing machines which are not yet depreciated.
>If running the MRI machine cost $100, people would do it.
There are different kinds of MRIs, but the actual direct costs for running an MRI without preparatory procedures is around $100 (preparatory dye injection may be another $50 cost). Marginal costs are lower still.