I bought a really night fixed/plunge combo years ago. Probably used it for a total of 7 projects in about 10 years, but every time I use it I tell myself, "I am SO glad that I bought this."
Of note, 4 of those 7 projects have been in the last 2.5 years, and 3 of those 4 are related to my current home theater. (Subwoofer build where I used the router for ALL sorts of things like cutting clean holes in braces, cutting holes for the tube port and driver, rounding a few edges, cutting groves over the joints so that I could fill them and not have seams showing, etc), another was my panels as mentioned above, another was for my riser, doing a roundover on the overhang for the carpet.
Before that I used it on 2 MAME arcade cabinets that I built to cut slots for T-molding, plus flush cutting the laminate for the covering on my latest, and the plunge router to cut out joystick holes and such. Plus a couple of other odd projects. Great tool, but yes, they can cost a chunk if you don't use them more than once.