so the UPS won't add any value, unless it happens to be able to provide power longer than the outage
True but the outage I mentioned was less than a second. The guy is now faced with a recovery bill of something in excess of $500.
Of course, if there's nothing unique on the drive (and there shouldn't be) then it doesn't really matter if it gets trashed. However, a £100 UPS will probably give you ten minute protection for the next 5 years (i.e. until the battery needs replacing) so you need to decide whether it's necessary or worth it.