The filters are MERV-14, not HEPA, so they're much cheaper ("materials for one fan are nine MERV-14 filters for $110"). See https://www.jefftk.com/p/merv-filter

The filters are MERV-14, not HEPA, so they're much cheaper ("materials for one fan are nine MERV-14 filters for $110"). See https://www.jefftk.com/p/merv-filters-for-covid https://www.jefftk.com/p/merv-filters-for-covid for why MERV-14.