the problem, rasputin, is the customs office.
in portugal they have quite an enormous power - they can open any letter or parcel that comes from outside the european union and thay can decide the value of the item inside.
even if it comes with an invoice with the price you paid, they can decide that the value is different and tax it more or less as they want.
it is a sad business...
I just got stung on a shipment from the US to the UK, though not entirely unexpectedly. A package valued at $50 cost me an extra $25 (actually £12.22) to receive, because the limit is £18 value for non-gift items, or £36 for gifts.
The actual VAT charge was £4.22, which is correct (at 17.5%) on the goods inside - but there is also an £8 charge for the "Royal Mail International Clearance Fee" - i.e. for calculating the charge and charging you.
If people are prepared to trade then the £36 limit is quite generous.
My lesson is not to buy big lots off eBay because they're not as cheap as buying singly.