Use paid journey groups
A bus-to-subway connection may share one integrated fare when transfer rules are satisfied. Counting two boardings as two full base fares overstates T-money cost and makes the pass look artificially attractive.
Include acquisition cost fairly
If you own neither card, include the physical card cost on both sides. If you already have one, remove that side’s acquisition cost. The comparison tool exposes both toggles so returning visitors receive a different answer from first-time visitors.
Test a conservative coverage case
Run the calculator at 100% eligible, then at 75% if your itinerary includes boundary stations or uncertain services. If the winner changes easily, choose based on convenience and coverage rather than a small estimated saving.