A few months ago, when Apple unveiled new MacBooks, I loaded the Apple Store website with my credit card ready. My wife’s ancient laptop was on the fritz, and a modern machine would make a nice gift. I found a MacBook Air for $760 — a bargain! — and ordered it with gusto. Plenty of us are reeling from ever-rising prices of consumer electronics driven by industrywide shortages of memory components, so I’ll let you in on a secret.