Just remember that your US customers with orders over $200 will have to pay duty and possibly taxes on the shipment.
I think the UK has a lower level for free entry as well, maybe $60 ( although, except for the US, that won't make a difference).
I agree that the CP rates are completely out of line - for a trading nation, it doesn't make sense for our post office to work against the exporters.
Imagination will often carry us to worlds that never were. But without it we go nowhere. Carl Sagan