Reduce price for less time
Will they pay more if you take longer?
I would say to customer
you can't have it both ways ..
Did that kind of work in London for over ten years , Richmond and Kew. If the are loaded ( most are, but claim poverty ) then you just give them 2 -8 week scale, ball part figure, depends, on the job obviesly, whatever part figure , per day , it was then for 8 hours = £ 280.00, plus the materrials cost. Duplicate receipts from suppliers.
IT WILL NEVER BE QUICKER THAN FIRST IMPRESSIONS, THATS THE NATURE OF THE BEAST! Make sure they are aware of that too. So, basiclly ball part plus 10% for the buggeration facter. If you don't f**k them about and turn out good work there will be no problems and their friends will start to call you in a sort off " begging /pleading manner"
! But be cool, don't say" you can't have it both ways", they won't get it, or trust it that way, and, ultimitly, they want the same as you, fair job for a fair price , thats it mate! Good luck !