See the pattern here
£4.50
£3.60 £4.20
£4.90
£3.10
£2.70 £3.10
£3.10 £3.50
£15.80 £17.60
£3.90 £4.50
£4.25 £4.90
£4.40 £4.90
£4.20 £4.90
£4.05 £4.50