The most cost-effective tape is BondTape or gummed Kraft paper tape. It takes less tape to create a secure seal with water-activated tape. Just one strip is all that is needed for a cardboard carton. Other tapes need more applications to create security, sometimes adding cross-directional strips to anchor the flaps of the carton down. Also, because gummed paper tapes are tamper-evident it is less likely your goods will slip out and get damaged, or worse, stolen.
Another cost-saving is that water-activated tape dispensers are benchtop mechanisms which prevents repetitive arm and hand movement. Staff are less likely to need sick leave for repetitive strain injury. Continuous use of a tape gun, some of which can be heavy, cause carpal tunnel, injury and the need for paid sick leave. This may also lead to you having to hire temporary staff to fulfil orders and keep your production up to speed.