Two wrongs don't make a "right". If the shipping companies are lying and fudging the specs and fees, does that make it ok for the Customer to do the same? That turns into a mess. If official representatives in a company are doing this, they should be called on it, and lose their jobs, possibly charged.
I agree, companies big or small have no right to squeeze money from customers using bogus measurements, weights, or Customs formula's. I've been dissatisfied with inaccurate and unfair taxes levied on used goods ( antiques) imported for years. Often times the item is over 50 years old should be duty free. Also it has usually been taxed multiple times so should not be re-taxed. Then there are bogus broker and handling fees attached. If it can be proven that the item is not available in the country you reside, then it should be clear to import without any fees. Free Trade ( agreement between Canada and the U.S.A.) doesn't apply to the "little guy". The fees and red tape I went through to import a 1957 Nash were insane!! Cheers!