I agree with everyone else - I usually just put a few line items for clothes, gifts, etc. and leave it at that.

On our last trip, I put down $1400 for the total, but that was a single form for both me and my husband. The customs officer said, "$1400? someone had fun shopping!" and sent us on our way. So I think the $800 exemption must apply to each individual.

However, I did spend $950 on another trip by myself and the customs officer just waved me through. So maybe the customs officers in JFK really like me or something.