There is no loss, money just go from one bank account to another and Bitcoins from one adress to another.
The amount of money in banks stay the same.
yep this is so true i was a bit stupid...
But I'm asking you that because a friend ask me who is loosing the profit we make?
When i buy a btc with some euro, does it mean euro loose some value? If nobody loose, then there is another problem, it mean we are creating wealth. but i don't think so!
Is the loss on transaction fee an explanation? i doubt that.
[EDIT] i think i answer to myself, we just don't make any profit. We make profit if we sell the bitcoins but if everybody sell, then btc price goes back to 0. And some will loose, some will win.
Once upon a time there was no USA (or, if you prefer, no France or Peru). When the USA came into being the dollar was created, and all dollar-denominated profits from that new country - profits which hadn't existed before - came into being with it.
Who were those profits taken from? Nobody. The USA (or France, or Peru)
created new wealth.
Same with bitcoin, I think. At least in many cases. As new use-cases for bitcoin are invented, new wealth will be created. As bitcoin is discovered to be more efficient in pre-existing use-cases, profits denominated in other currencies will be taken by bitcoin.
But overall, I believe your original question ("So is there a way to compute this loss?") is not fully valid.