It does cost him. More people would know of MINIX and more would have heard of its creator. More people would buy his books, hire him for consulting on OS design, etc.
US copyright law lets you sue for either actual damages plus the infringer's profits OR statutory damages.
The first good faith claim to do is to notice Intel to add the copyright notice.
It's rather late now, though, considering it's been around for years now without anyone knowing exactly because they did not include that copyright notice.
I have no idea what copyright law says about damages in a case where the infringing party tries to keep their large-scale infringement secret.
The statutory damages option discussed above does not require a showing of actualy damages. It's just x dollars times the number of instances of infringement. Also, while delay in providing notice of infringement can work against the copyright owner, in this case, because Intel is a sophisticated party (i.e., big company with many in house lawyers and outside law firms advising them), the delay in making a claim would likely not help Intel's case.
Beyond the valid complaint of this being a personal insult, that is.