Barring deliberate cost saving measures, consider something like electricity costs. Your electric use is probably pretty consistent whether the price is $0.10 or $0.15 per kWh (ok, perhaps not yours, but average across the economy). Depending on your environment and what you do, you have to run your fridge, you have to run your AC/heat, you have to turn on lights, you have to manufacture your goods (if you're a business and want to stay in business). The same (roughly) amount of electricity will be used regardless of the cost.

If electricity suddenly drops in cost by 50%, then money you expected to spend on electricity is now being left in your accounts. There's been no actual shift, but the expected movement of money has been altered.