There's also the fact that you have to pay execs generously to be able to compete with private sector execs.
Suppose I'm someone capable of being a manager. If the private sector will pay me $300k/year, but the public sector will only pay me $100k/year, then I'm going to try and work for the private sector if I can! Every applicant is going to try the private sector posting first, and the good ones will get the private sector jobs.. and the government will be left with those who the private sector employer rejected, in other words, the bottom of the barrel.
The constant populist rage against "well paid flashy execs" and the resulting cuts to their salaries is a big part of the reason why government is so much less efficient and so much more blundering than private business.
Most public sector employees aren't executives or even highly skilled professionals. Quite a few of them get high wages, simply because of extensive union protection backed by a virtually inexhaustible revenue source (the taxpayer).
I'm in the air force. When I got posted to Ottawa as a newly trained Lieutenant with 2 years of training and a 4 year undergraduate degree in aerospace e engineering, I discovered the section's admin assistant with high school and 5 years experience made more than me. The portion of the project I covered was worth at least $200 million. And failure of that system in the field could result in lives lost (airborne sensors and comms for a search and rescue platform).
Working with intelligence analysts, I later found out that they were in the same union as the admin assistants. The latter group actively fought the reclassification of the intelligence analysts (all of whom had MAs as a minimum), because their inclusion in the same group or bargaining unit, improved the odds of the admin assistants getting better raises.
What I learned about the public service from my experience? Professional staff are usually underpaid compared to industry. Their benefits and vacation make up for the disparity. Support staff, on the other hand, get pay and benefits significantly beyond what any of them would in industry. And that's not something the public is really blind towards.
Or let's talk about teachers. You have hoardes of young people who can't get jobs because the long tenure staff won't retire. There's no real threat of performance based dismissal unless you're atrocious. 11 weeks of vacation in total. Six figure salary at the top end. One of the best pension plans in the country. Now, I'm not one that is opposed to paying good teachers well (and I've dated one and married one) but it's hard to argue that we reward good teachers well, as opposed to providing a really lucrative public service career for people who probably wouldn't make as much in the private sector. For what we pay teachers, I would expect standards on par with the Finns (all teachers have MEd with very strong mentorship and training programs). Is it that hard to understand why the public might get peeved when teachers threaten strikes?
Now, overall, much of the wage disparity is simply owing to the collapse of the unionisation and the rise of freelancing in the private sector. However, that's just not going to reassure the public that public sector wages and wage increases are justified, when their wages are stagnant and they have to pay higher taxes to support those wages, benefits and increases far beyond anything they can hope to receive.
