No estimate has been made. Many routes do not have advance purchase tickets and where they do they vary considerably in price and quota availability.
Unregulated fares are a matter for individual train operating companies. Fares policy relating to unregulated fares has not been amended as a result of the South Central franchise replacement. In this case, the winner's bid is based on unregulated fares increasing on average by RPI +1 per cent. across the life of the franchise, but this is not a contractual commitment.
The Department for Transport has not assessed the cost implications of limiting unregulated fare increases.