What do I mean by that? Well, let's take a look at Enemy #1 in this regard: load screens.
For me personally, I can't stand load screens or waiting on my computer for processing. I'll go out of my way to spend hundreds of extra dollars on my PC build to avoid them because time is a valuable commodity when it comes to getting work done.
Picture a typical work day of using your Intel Core2 Duo computer that's several years old, but still works, so management has yet to upgrade it. Sitting at load screens for 5-10 seconds throughout the day is pretty normal, and you've managed to justify multiple water/coffee breaks because of it. Multitasking things is also out of the question, since you can't push the PC too hard without it locking up temporarily, then waiting for it to catch up.
For Enemy #2, consider the infamous "necessary reboot".
You've probably hit this one at some point - you have to reboot your computer because it starts randomly locking up or slows down to an unrecoverable crawl. For some, this is a weekly occurrence; for others, it's a daily one.
If you have 10-second wait times an average of 30 times a day, for example, you're losing 5 minutes of time each day to having a slow PC. That adds up to roughly 1.75 hours each month, or 21 hours each year if you're the average full-time employee. In other words, that slow PC is costing the company $273 per year, which they could have invested to get you a faster PC.
$273 can kill a lot of load screens if used correctly on a PC build.
This doesn't factor in the shared time loss of if the employee in question calls the helpdesk to complain about their slow PC, in which case the technician might be able to speed it up slightly, but will still ultimately be limited by the hardware's performance. Their time-to-dollars used in this regard counts as a potential earnings loss for the company as well.
People enjoy having nice toys, and having great computers offers a great ROI for the additional cost involved.