Prompted by a discussion on the Seeking Alpha about how RDSB would be a buy for an individual if it fell below $60 again I was somewhat confused. I thought it sounded a lot more expensive than the current LSE price and it is. At time of writing LSE RDSB is £23.07, while on NYSE it’s $61.33 (approx £48.86, so roughly twice the LSE price).

My very basic Googling around the subject suggests pricing should pretty much equilibriate across markets so what gives here? Is a NYSE “share” of Shell two times the “share” of the company that is purchased on the LSE. I would have assumed not and that the shares of the same company and class purchased on different exchanges would be essentially fungible, but I think I must be missing an important fundamental point here. Can anyone shed any light?