Elliot uses a Dell...

Also he uses a non-existant "E Computer"

^^^ftw!

All desktop PCs have parts that don't [necessarily] cost a fortune to replace, because PC parts are non-proprietary, though, ironically, off-the-shelf brands like Dell and others sometimes use non-standard parts which make them more of a pain in the ass to fix. For example, a Dell (or HP, or whatever) PC might have a weird small form factor power supply instead of a standard ATX power supply, and/or it might have a weird pinout that won't plug into a standard ATX motherboard.

I don't consider anyone who "swears by" off-the-shelf PCs to be much of a "computer guy". A typical off-the-shelf PC has a case that won't accept a larger form factor motherboard than what it came with, and won't have plugs for the power switch, reset switch, power LED, HDD LED, etc., that are configurable for the wide variety of header configurations that you'll find on various motherboards. They also might not accommodate a standard ATX power supply, they are usually light on drive bays and motherboard expansion slots, and the BIOS usually doesn't have any overclocking functionality.

A "computer guy" normally builds his own PC (at least with regard to his main desktop PC), because that allows you to choose every part (meaning you don't get stuck with whatever lowest-bidder OEM parts came with an off-the-shelf PC), and you get a case that's designed to work with standard ATX power supplies and motherboards, and has plenty of drive bays. After you've built your initial PC, upgrading is a lot easier, because you can just, e.g., replace the motherboard, CPU, and RAM, without the roadblocks that you often encounter when trying to do that with an off-the-shelf PC. And since Elliot routinely destroys his hardware (including stuff that is utterly pointless to destroy, like motherboards and RAM) and then rebuilds with new hardware, it makes no sense that he would have a Dell case rather than a far more versatile aftermarket case.

My current main PC has a big Chenming 601 case that I bought in 2006, a power supply that I bought in 2010, a motherboard/CPU/RAM that I bought in 2015, a hard drive that I bought in 2014, a video card that I bought in 2013, and an SSD that I bought in 2018.