Again, how can 5% (5 BTC) possibly be equal to 2.06% (2.06 BTC) when we're talking about the same thing (profit) over the same time period (a week) when both are using the same variable (wagered amount)? How much is in the investment pool is irrelevant to any of this discussion.
No they're not using the same variable. When you invest you buy a percentage of the profits. This is totally independent of the amount wagered and actual profit/loss. They're two different numbers which gives you two different denominators when calculating the percents.
Also, a lot of the wagered coins aren't really different coins. I bet one coin, win. I have two coins. Bet another coin. Lose. Bet another coin. Lose. That's 3 BTC worth of bets when only two real coins ever existed. So 1000 bitcoin bet doesn't mean that someone transferred 1000 bitcoin.