It costs nothing in the UK as it's covered under the National Health Service. Well - I say "nothing". All British citizens pay "national insurance", but it's effectively a regressive tax that's not based on the individual's health (as insurance would be), so some folks are effectively subsidising others. To give you an idea of cost, my NI contributions are about ~5.5% of my salary, but that also goes towards the state pension.

All that said, it's not a massive cheap free-for-all on medication - in the UK we've still got hospital/NHS trust budgets which have been iteratively slashed by a decade of successively worse Conservative governments, so generally the inclination is for the NHS to prescribe the (much) cheaper generics.