As part of the fares revision last month, TfL increased the deposit on new Oyster cards from £3 to £5. This is what you’ll pay online, at Oyster ticket stops and at station ticket offices. The deposit is refundable of course, but only when you surrender the card. However, at many underground stations there are small blue vending machines which dispense an Oyster card with £2 PAYG balance in return for £5 in coins. The difference is the deposit, which is logged on the card so you can’t claim £5 if you only paid £3. I guess they’ll get round to changing the machines eventually, but for now they seem an ideal way to avoid having an extra £2 tied up on the card.