I wouldn't mind so much if it wasn't such a crapshoot. Sometimes you pay no duty sometimes you get hit. Sometimes the firm that delivers charges a fee for collecting the tax, sometimes not. Sometimes you have to go to a mail depot to collect the item + pay the tax, sometimes you have to pay at your door, sometimes you get invoiced after the event.

I seem to remember a private delivery firm once charged me a £15 fee for collecting £5 in tax!

Be careful about putting a low value on the paperwork. I'm sure Customs would be quite happy to impound and destroy the goods if they find out.