The legal standard will be related. Absent a written deal, the court would look at what the customer would have or should have reasonably expected, based on typical rates for such work, the value and cost of doing the work, etc. It can get quite messy and usually it's not worthwhile litigating such a thing.
(heck, even with a written deal, the fine print often matters less that people might think in court, though a badly written contract will sure draw out much more protracted arguments about such details)
(heck, even with a written deal, the fine print often matters less that people might think in court, though a badly written contract will sure draw out much more protracted arguments about such details)