An American who sold cotton in Liverpool at the high price point got $1.89 in Greenbacks per pound (less shipping costs), which was over fourteen times the amount he would have received in common US currency before the war. The documentation is repeated below.The British price approximately quadrupled. The increase in the US was larger because of inflation.
Your prices in Pence above are only averages.
James L. Watkins' King Cotton (page 30) shows that the Liverpool price got as high as 31.5 Pence, which was in June 1864* when a Greenback dollar was worth only $0.35. ($2.85 Greenbacks = One Gold Dollar.) Each British Pound was worth about $5.00 in gold and there were 240 Pence in each Pound. Thus, each pence was worth $0.021 in gold. Therefore, the high Liverpool price in terms of gold dollars was $0.66, which was equivalent to $1.89 Greenbacks, then the dominant currency in the Federal Union.
*Jay Sexton, Debtor Diplomacy, 128