"I've been working in a nursery for a while now and have decided to become a nanny." - That could mean a variety of things, from working for a few months, to working for many years. It tells us nothing useful - nothing about how senior the person is within the nursery, what age ranges they have worked with, or how much support they need from colleagues.
Being a nanny I feel is quite different to working in a nursery. I'm sure some of us regulars on here could post a list of all the differences - but I really can't be bothered.
The major difference in my view is that in the nursery environment there are more adults around so when things get tough, there are other adults to talk with, get support from, even to cover for a while if someone needs a break. Nannies are on their own... they have no backup, no support, nothing. If things start going wrong, they need to be able to handle things, need to use a common sense approach and adapt quickly to the situation. While the child's parents may be at the end of a phone, they could be some hours travelling distance away, they may not be contactable for periods of time etc. A nanny has to cope with whatever arises, whereas in a nursery setting there are other adults to help out.
Nurseries often pay staff very low wages, typically NMW (some may be on Development rate). Therefore any salary above that is a payrise. If the person is aged 22 or above, then NMW is currently £5.73. If they were offered a job at £6, then that is just under a 5% rise. If offered a job at £7, then that is a little over a 22% rise. I think most of us would be happy with a 22% payrise when changing jobs - sure some people may want more than that, but I don't feel that 22% is that bad.
If a nanny worked 50 hours per week and was paid £7 gross per hour, then that's £18200 gross per year. Employers NI is another £1633 roughly, meaning that the employer has to find just under £20,000 from their own take home pay... and this is before any other expenses. You can do the calculations yourself with the help of ListenToTaxman and E-Gismos.
Will parents who earn large amounts pay more for childcare? Perhaps they will to a certain extent but my view is that parents who have higher incomes also tend to have higher expenses - high travel to work costs (due to working in a city for example), a bigger house (often meaning a bigger mortgage), a more luxury car (often still on finance), private school fees, higher pension contributions, savings/investments for their children. Yes they could cut down on some costs perhaps, but why should they? They earn the money so decide how they wish to spend that.
If that means they pay their nanny an average wage, but buy the nanny a nice Birthday/Xmas present, give a 'good service' bonus, don't restrict the nanny in terms of weekly mileage/weekly kitty, provide the nanny with a nice place to work in, plentiful food supply, then so be it... the nanny has nice working conditions and a job they like.