Not_a_boffin,
Steel is currently significantly less than £200 a tonne. Try £155 to £175. The added cost of cutting up and separating what has already been used, plus transportation has to be taken in to account.
What people sometimes forget is that the raw materials are actually a very small part of the costs for a project. It's the cutting, shaping and fabricating that cost, plus man hours, design and BAEs rip off prices. The political decisions by both labour and the Conservatives have added significantly to the overall costs. Building in different yards hasn't helped.
I believe that the costs for emals is at the upper end of the scale. Mind you the costs are probably realistic as something will go wrong, the politicians will change their mind etc.