Really depends on the reasoner in use. I'd really take most current public benchmarks on reasoner performance with a grain of salt, as most implementations out

Really depends on the reasoner in use. I'd really take most current public benchmarks on reasoner performance with a grain of salt, as most implementations out there are mostly academic-grade non-production systems. E.g. Stardog does most of their reasoning via query rewriting (and also lean on some restrictions). That way you can leverage DBs to do what they are good at. If you can then on top of that build some clever caching or incremental computation, you should be fine for even pretty huge dataset sizes.