I'm not entirely sure that Britcoin does the trading correctly, but I've found it difficulty to confirm as the market moves so quickly.
Let's say there are three open bids:
PRICE BTC Wanted
10 1
9 1
8 1
Let's then say I create an offer of 3 BTC for 24 GBP. This should be read as "3 BTC for
at most 30GBP". This offer will eat up these three bids.
1 * 10 + 1 * 9 + 1 * 8 = 27 GBP
Not 30GBP.
The reason it should be like this is that there is nothing to stop me entering the three asks one at a time, so it's just a shortcut.
As far as I can tell, whenever I have executed trades like this, I have always been charged the full 30GBP. i.e. I get exactly what I offered.
The problem is, I'm not sure where the difference goes. The people offering those bids also get what they asked for: 27GBP. So where did the 3GBP difference go?
As I say, perhaps I've misunderstood, it's not easy to be sure when there are bids and asks appearing while you're creating your own bids and asks.