Its an absolute minefield, its been clogging up the window cleaning forum for years. Basically if there is another alternative, irrespective of price, you cant use a ladder. Lets face it there is always an alternative, hire a cherry picker or a tower. But I'm not getting into all that again. Have a look on the WC forum for a taster.
So you quote a price based on what you see as legal best practice and you don't get any jobs. Next time you drive past you see a couple of Polish blokes hanging off a couple of unsecured ladder doing the job for half the price you quoted.