Shipping charge for CU FT more than the real amount

I shipped my items from the UK to the USA.  The moving charged me for shipping 380 CU FT.

Because the contained was inspected at US customs I had to pay for my part of the container.  I was charged for 250 CU FT.

So I see a difference of 130 CU FT between the movers and the customs measurements.

Have the shipping company just ripped me off ?  Or is there some other things I need to consider ?

Thanks

Was the weight possibly a factor? 

Was there any irregularity in the size of the shipment? I know when my stuff was "calculated" for cubic feet they took the longest measurement by the longest measurement - even if it didn't actually take up the *whole* volume.

Was the weight possibly a factor? 

No I do not believe that they used the weight.  At least it was not in the paper work.

Was there any irregularity in the size of the shipment? I know when my stuff was "calculated" for cubic feet they took the longest measurement by the longest measurement - even if it didn't actually take up the *whole* volume.

Interesting, but the furniture was oblong and one round small piece.  Thanks for the input.