For bigmac it's not a big deal, but for investment it is. Imagine your company have 10 millions in cash, you could invest on a new machine to produce more (or better quality, or cheaper). But if you knew that the machine was going to cost you only 9 millions in 3 months. Will you buy it now even though you know it's only going to make you earn 300k in 3 months ? Of course not, you'll wait those 3 months. This is the problem with deflation, nobody wants to invest and people delay or reduce consumption. this really harms the economy.