At least here in germany we use Cat.7 in general since, it feels like forever, at least in the last 10 years I saw/used nothing else on a new install. I know stuff is different in especially the US, but well, US power system…I think we better stop here.
The big thing with fiber is not the cabling, but the termination. So if you can terminate yourself/get it extremely cheap, or use patch cables and coupler wall plates you could maybe get cheaper.
The cost of termination is so high and specialized, for the most buildings they even use pre-terminated cables for your fiber patchpanels in the rack. Cat7 is more expensive than Cat5 here, but not by such a big extent. And, thats one of the biggest points, its easier to get as for example Cat6.