Under cut him and then dump his customers.
Tell all his new customers he has Swine Flu.
Give him a call and book him to do your house and then don't pay him.
Failing that just shake him off his ladder when he's up it.
I know his prices are boardering on the ridiculous but he'll learn soon enough I guess. Christ they sound the sort of prices I hear old ladies telling me that their old window cleaner used to charge ...... in1971 :
And I thought we were quite cheap