Same thing happened to my wife and I returning to the US in Miami after a Caribbean cruise (we're US citizens by the way). My wife purchased some earrings costing roughly $2,000. Back then we had to fill out customs forms and even though she had purchased the jewelry in St. Thomas (a US territory) she declared them.
Miami customs pulled us out of line and sent us to a separate room where we waited for way more than an hour for someone to come in and process us. They went through each piece of luggage examining everything in our suitcases, carry-ons and backpack. I had to turn out my pockets as well. Then we had to repack everything ourselves. There was no apology, no lecture, nothing; just a "You're free to go." She has purchased jewelry since then on subsequent cruises but now wears them through customs and doesn't say a thing.