Look at your industry. Have the economics changed due to technology, fuel, tax, finance?
Look at the components of the Return on Investment (ROI) in your world. The denominator will be the investment by your customer. What often happens over time is that the benefits rise relative to the price point or investment. So when you add up the benefits together to arrive at the nominator, you might find the ROI % has changed dramatically.
I believe in this economy more than ever, prospects need help converting value propositions to improved performance to ROI%.