An invitation mentions an inexpensive ticket. Transport, accommodation and meals may make the full occasion a much larger expense.
Estimate the costs that accepting would create for you. Ask about details that are still uncertain, such as location or expected contributions. You can request time to check before giving a firm answer.
Offer a workable version
If the full plan does not fit, consider whether you can join for part of it or suggest a simpler alternative. Say what you can manage clearly. There is no need to disclose private account details to explain that an expense is outside your current budget.
Once you accept, keep the expected cost with the event in your planning notes. If the arrangement changes substantially, discuss it again instead of treating the original yes as agreement to every later addition. For group plans, an early conversation about price ranges helps everyone choose before reservations are made. It can also reveal that others would prefer a less expensive option.
