A HIRED firm of economic boffins is arguing that Railtrack is worth just £200m at most, equivalent to less than 40p a share. Nera Economic Consulting, part of the Mercer Consulting Group, has drawn up a report in preparation for the Government's sale of Railtrack. Nera has run several economic models, concluding Railtrack's equity value ranges from £200m at best to minus £2.5bn in the worst case scenario.