My wife is Indonesian and always wants to go home to visit her parents, but the cost is high. How do we arrange it fairly?

Your wife's wish to visit her parents deserves respect; what needs planning is how often and the cost, not whether she may go. She left her family to build a home with you, and that longing is part of her sacrifice. Sit down together and set an annual budget for going home, for example one trip a year plus a video call every week. Save a little each month in a special account so that the trip does not become a sudden burden. If the cost does not yet allow it, find other ways such as inviting her parents to come here now and then. Most importantly, your wife knows that you understand her longing. See Muslim families in Indonesia.