I had a similar one last week. Went to quote, £80 first clean and £60 8 weekly.
She was a bit shocked and said it is double what she was paying, but that her old window cleaner was unreliable. After a few questions it turns out she's a messer. Gate not unlocked for them, wanting to change frequencies etc. She said she would go for the first clean 'and see how we get on' - I haven't got back to her and won't. It will always happen from time to time.
There's lots of good work out there, it just depends if you're desperate for any work and constantly need new jobs or can spend a bit more time but get quality customers.