If you want to boldly go where no market has gone before you'll need a way to pay for it.
Travelex, the foreign exchange company, has developed a currency for space. The Quasi Universal Intergalactic Denomination ("Quid") - which looks a little like a squashed Teflon egg - avoids the problems of coins (sharp edges), bank cards (allergic to cosmic radiation) and credit transfer (shops selling tourist tat on Mars would have to wait an hour to contact your local bank). Travelex has also thoughtfully applied to open a bureau de change on the moon.
But before you rush off to buy your exciting new currency, you might need a chat with your bank manager. A ticket for an afternoon in space with Virgin Galactic will knock you back an astronomical £200,000.