Can you explain VAT refunds and paying US customs?

[parisinthespring]

So, I still don't fully understand it, but I bought a few things that I needed to claim VAT on in Paris last month. I bought my purse at a department store that had a VAT desk, so they filled out the paperwork for me, all I had to do was present my paperwork and item at the desk at the airport. The refund will apparently appear on my credit card at some point. You do not get the entire 22% back, I believe it is around 12%. If it had been 22, I would have come home with another bag! Make sure you bring your passport to the store with you, I didn't when I made an impromptu purchase one day and no refund for me.
As for US Customs I put the value in USD that I paid for my items. I was a bit over and they just told me to go on through. Being $400 over the guy told me it would be like $30, I have no idea if that is right or not, he seemed kind of like he just didn't care.