Going rates for hongbao
not attending ceremony: NT$1200 (US$37)
attending ceremony: NT$1600 (US$50)
attending ceremony with guest: $1800 (US$56)
But of course you get something in return. You get a box of cookies. And the other party will be required to return the favor at your own wedding and the weddings of all your children. I'm not sure, but they are probably also obligated to send you money for your children's manyue (滿月) (one-month old) celebration. Going rates for that are NT$500-NT$600 (US$15.50 - $18.60) , although close friends or wealthy aquaintances might give NT$1000. And of course, you get something in return: oily glutinous rice (油飯), and possibly red hard-boiled eggs, cake, fried chicken, and rice-wine (?) chicken soup (雞酒).
One of the invitees to the engagement ceremony was a new coworker who has probably never even talked to the coworker who is getting engaged. When asked, he said that he gave NT$1600, and he would not attend the ceremony because he hardly knows her. When everyone else heard this, they laughed at him and berated him for his foolishness. Everyone knows that he only needed to give $1200! He went to see if he could get his red envelope back and remove the excess $400. But it was too late.
What's the price for opting out of all this reciprocity? It sounds a little dangerous, but I think I'm going to find out.