That saving moves a cost.
Shorter hours reduce staffing costs. They also push the study group into a café where people would have to buy something.
Nexo asks
Does the cost disappear, or move from the room’s budget to its users?
Try one response
The cost may move to users instead of disappearing. You need to consider who pays and how much.
Try another response
The tradeoff becomes visible, even if the group still has to make a difficult choice.
Make something useful
List costs to the operator and costs to users separately.
Tell a friend
The room saves money. Some users may spend more elsewhere. Both effects belong in the comparison.
Say it your way. Keep the supported meaning and the part you still need to check.