No one is immune to a bargain — not even those who can spend GBP 30,000 on a watch. At Watches of Switzerland, an authorised dealer, an Audemars Piguet Royal Oak automatic in rose gold sells for GBP 42,600, but the same watch is on offer at "grey market" website Chrono24 from US dealer Watch My Diamonds for USD 34,850 (GBP 27,227). It is impossible to ignore that the grey market is becoming a powerful force in the watch industry, which is worth USD 62.5bn, according to Euromonitor.

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