Value, margins, and psychology.
Know something useful about pricing?
Cost-plus pricing (hours × rate + margin) creates a perverse incentive: the faster you get, the less you earn. Value-based pricing, as defined by Baker (Pricing on Purpose, 2006), prices the transformation rather than the inputs. Discovery question: "What does this problem cost you per month?" If the answer is $10K/month, a $12K project fee represents a 10:1 ROI in year one.
