Actually, most transactions are under 100 btc, and easily a third of those are less than 10btc. Just watch bitcoinmonitor.com to see this.
When large accounts move a boatload of coins around, it skews all those averages you're calculating. So Synaptic, how do you like them apples?! =)
Exactly. The 'average' they are talking about is the mean but median and mode are probably much more helpful averages.
Maybe round all transactions to the nearest BTC (chop off the fractions) and then group together... what's the most common transaction size then?