VAT/taxes on personal ex-EU import of computer hardware

If I was to order, say, a hard disk drive via eBay from a US or other ex-EU seller for €80 + €20 P&P then what VAT or other taxes would be payable on import assuming that these are not charged by the seller?

You would have to pay import duties and VAT @21%

rate of Import Futies can be found [broken link removed]

High levelsummer found [broken link removed]

Thanks - would the 21% be levied on the item price (e.g. €80 in this case), the total transaction cost (e.g. €100 in this case) or some nominal value put on the goods by Revenue if they decided that the item price paid was "too low" compared to the price locally or something like that?