The costs of employing people are not limited to the wage you pay them.....the costs are greater for the employer than you would realise, on average the cost to the employer is twice what the gross wage to the individual is.
To employ two people at lower minumum wage rates is far more costly than employing a single person on the higher rate.....and that is without costing the extra involvment in training and supervisory management that younger people on average require.
With respect, you don't understand how a business works or the inherrent costs of employing someone, especially with regard to employers contributions to the HMRC, Statutory Provisions, Pension etc.....