Responding to a destination-wedding invitation is a bigger decision than a local one. You are committing to a flight, three nights of accommodation, and $1,500–$4,500 in total costs. The couple needs your response quickly; you need to think it through. Both can be true.
The answer to "should I go" is almost always yes if you can afford it and clear the dates. Destination weddings are memorable because the guest list is smaller, the programme is longer, and the trip itself is a gift. But affordability and logistics are real constraints, and declining gracefully is a perfectly acceptable choice.