If I use Oyster PAYG to travel into London by train and continue to a Zone 1 destination by underground the underground leg is free, but if I continue by bus it costs extra. For example: Wembley Stadium to Regents Park via Chiltern (Marylebone) + Bakerloo line = £3.90 in peak; but via Chiltern + 453 bus it is £5.40. Is this correct? TfL incentivises use of underground rather than bus for the last mile?