Wouldn't be surprised if a lot of the time is spent loading and unloading Inkscape. That said, I can't imagine even a moderate batch conversion/export job only

Wouldn't be surprised if a lot of the time is spent loading and unloading Inkscape. That said, I can't imagine even a moderate batch conversion/export job only taking a few hundred milliseconds unless it's somehow barely doing any work, or the total file size of all exports/renders is pretty small.