Even big companies fall into the trap -- pursuing market share and underestimating new customer acquisition costs. American auto makers such as GM fell into this trap, building cars and offering discounts in the pursuit of market-share. Eventually, the cost of acquiring customers was greater than the profit they generated. As a freelancer, it's also easy to focus on the big numbers: hourly rate and total income. But are you measuring your customer acquisition costs?
Giving your top customers occaisional free and delightful extra help can actually pay more in the long run! Keep in mind how much it costs to get a new customer vs. cementing a longer relationship with an existing one. Sometimes, donating a couple of hours in the name of building relationships is actually the fiscally sound choice!