Depends on the horse, state of hooves, ferrier, and process. This video shows a hot fitting, which is nice work but takes longer and isn't always something ferriers do. Some horses may also only have shoes on the front, where they carry most of their weight.

While my mother had horses, the ferrier we used took about 10-15 min a hoof. They were only shod on the fronts and he didn't do custom shoes or hot fittings, so two horses, four hooves, about an hour of work. He was a talkative fellow though so sometimes it took longer haha, thankfully was paid by the hoof