Estimated cost when buying a share. How is this calculated? Stamp duty + something else?

[obrienciaran]

I think that 2 is to indicate compounding, as in you x2 your money. You can read more about it here.

I was told that I have to constantly sell my stock then reinvest it to "lock in" profits. Is this true?

While also misquoting what I told him in his original post, just to stir the pot even further.