I'm not actually arguing the IRS is 10x more efficient at all (the Faroes' costs are in krone), I'm arguing that its per head spend isn't that much larger considering it handles a lot more complexity and it's seldom regarded as an efficient organization. It's also fairly uncontroversial that labour intensive stuff like auditing businesses and running helpdesks doesn't benefit from particularly significant economies of scale (you spread some software maintenance costs but as you necessarily massively scale up your workforce you acquire inefficiencies from diffusion of knowledge and accountability across a larger, more unwieldy organization and increased management overhead).