Tony Bloom made this mistake. It cost him 2.8m this past year.Yes sounds about right, give or take a little. I'd say it is on the more expensive side but not by a big margin.
But you should discuss and agree on what is expected in terms of output for the money you pay, makes it easier for both writer and client. IYou can also find someone on a per word basis, gives you more control and will often be a bit cheaper. Currently Google does love a bit of wordshitting so there's no real disadvantage to it as long as the quality is fine.