If I were on a team of developers, and every new team member got a loaded Macbook Pro, and I were stuck with Ye Olde HP from 2007, I would feel pretty slighted. It's patently unfair that other devs would be seen as valuable enough to have excellent hardware, while I were consigned to the dregs. Even more so that he was expected to bring his own, rather than have tools provided by the employer, especially given that then were already doing that for every other one of his peers.
Of course, being an experienced developer, I know that the way to remedy that is not with complaints about fairness -- decision makers might not even have realized that was what I was using. Rather, pointing out the productivity benefits of having hardware similar to other devs usually seems to suffice. (Spec out a machine, propose it, etc.) It's not your machine, it's the company's, and it lets you be a more productive resource.
Maybe I misread, but I thought he bought a new computer WHILE he was interning. Not to back the company overall, but if he just bought a new computer I can understand why they might not spend the money on a new one for him when they extended the job offer - they know he just bought one, basic business sense.
edit: I wrestled with bringing this up, but you mention several times what kind of laptop you had versus what kind your coworkers had and that you bought an unaffordable laptop for a part time internship. You can usually find passable used laptops on craigslist and such that are very inexpensive. Getting by on one of those is a lot more impressive than a loaded out Macbook, so why should this have mattered to you?