It's hard to compete when you're basically a warehouse and your market is the literal population of the internet.
Yeah, microcenter, even if it's the only computer/electronics store for 100 miles, can still only hold so much, and they only reach people in/around their city at most. It's not like people are crossing state lines to get to a computer store.... Unless you live on the border of your state, I suppose.
Amazon has, at the very least, dozens of warehouses across the country that can deliver whatever it is you want with remarkable efficiency because postal/parcel services have been systematically improving over the past 50+ years.
I'm not saying I'm a fan of Amazon, but bluntly, is it really surprising, in the slightest, that Amazon can out price everyone else?