Yes, for close friends or relatives will give $800-1000. I have attended a few lunch wedding banquets, lunch sets are much cheaper than dinner (for Grand Hyatt, cost of cocktail around $400+ per person, and dinner $1100 per person), so $500 is enough for cocktails (as some places only charge $100-300+ per person).
Some cocktails only provide you a glass of champagne and some western dim sum or just a piece of cake, so $500 is a lot just eating the cake, haha. So maybe you can give a gift instead of cash. How abt a $100-200 photo frame?