Paul__B:
You have answered your own question!Not that I am in the US, but the situation is the same.
You are buying "cheap stuff",. Below a certain amount, it would cost more for them to attempt to collect duty on the items, than the duty collected. The amount is generally about $1000, but may be less. Certainly, collecting 10% duty on a $100 item is barely worth the paperwork (including opening the items and estimating value), especially as people are likely to dispute the value and it would just become bad "PR".
rofl you are not living in Belgium ]
We pay for collecting the custom guy to collect the money :~
On my custom invoices there is a line for customs and for duties.
Duties is mostly more than customs.