My son (US CITIZEN) marrying Chinese girlfriend

My son has been in China for 4 years and is marrying his Chinese girlfriend of 3 years. We went over and have met with her parents who are wonderful people. We agreed to pay for the wedding except the wedding bands, which they are paying for. We are also paying their airfare to come to the US for the ceremony here. There was no mention of the betrothal gift to the parents. Do you think this is still expected?
We cannot afford that on top of everything else!