Airports expansion costs higher than expected

The UK faces urgent airport capacity expansion needs, but the Airports Commission highlights underestimated costs. Past infrastructure projects show optimism bias, leading to a 20% cost buffer. Rejected proposals include Stansted and Thames Estuary, leaving options at Heathrow and Gatwick. Heathrow proposes a new runway and terminal for £14.8 billion or extending the northern runway for £10.1 billion. Gatwick suggests a new runway and terminal for £7.4 billion. Both airports justify their cost estimates, with Heathrow citing past successes. The Airports Commission awaits public feedback before making recommendations post-election.

What is the budgeted cost for the new three and a half kilometre runway and terminal at Heathrow?

What has the airport Commission stated regarding the public's response to the proposed airport expansions?