DO NOT BUDGE !!!!
You have priced the job. That's it.
If a customer is trying to play 2 window cleaners off against each other there will only be one winner.
And it won't be a window cleaner.
I must admit I was a bit naughty on this once. I was at a job talking to another window cleaner who I bumped into. He did a job about three houses away. Anyway, some guy came from the corner house and asked for a quote. When he realised we weren't working together he asked if we could each do a quote. No problem with that at all so far. However, he had asked me for a quote a few years before (I think he had forgotten) and I never heard from him. I may be wrong but I sensed that he might bwe a PITA customner so I didn't really want the job. So, after he went, I told the other cleaner what I felt and that I didn't want the job anyway so I worked it with him that he put in a really good price and I made mine a bit higher. I've no idea if he got the job or not but the windows were minging. They certainly hadn't been done since a long time before my original quote