"Zero dollar groups" has opposite meaning if we will talk about spending. For such groups tours to Thailand cost zero (or almost zero) because they have obligatory shopping in programs and must spend a lot - on this way tour operator covers expenses - via commissions from Thai shops.
Examples:
https://www.bangkokpost.com/business...lar-tour-costs
https://www.ft.com/content/698a002a-...b-680c49b4b4c0