Earlier quoted context omitted.
I say this as somebody who has worked vendor side in UK public sector for a number of years. It's policy. It's official Whitehall policy. As a department you can't hire programmers at £100k/year, because that pushes them way, way higher than civil service bands allow. But you can pay a "Systems Integrator" - a consultancy like Cap Gemini, Deloitte, Fujitsu - £600/day for the same programmer in the same seat. So, £100…
> So, £100k/year = bad, £120k/year via an external consultancy = good. Ding ding ding. This is all driven by ideological mistrust of the public sector, as you've pointed out and people are even defending in the comments.
FDR, who can hardly be accused of distrusting the public sector, emphasized the importance of public control over government sector salaries: https://www.fdrlibrary.org/unions