So I'd go with something like BTC 100 to BTC 3,000 for people having joined in 2011, with heavy emphasis towards the former.
Only about 1,000 Bitcoin downloads in all of 2009, so perhaps 100 active users. If some of them are still around, we can assume that they've had chance to mine huge
BTC and still hold. If they are not around, it is more likely that they have sold the majority.
About 17,000 downloads in 2010/1-6, but the price in OTC was still same. I believe the OTC market did not reflect the increased interest (or perhaps it did, but I don't have the data). At this point is was still possible to mine shitloads, but not as easily.
As price started to increase since the opening of Mt.Gox in July 2010, the difficulty also went up. It did not immediately feel a good idea to buy at the exchange as price was rising very rapidly. Many sold. (I watched price go up from about .25 to a hundredfold without buying).
Perhaps you are right - when Bitcoin was small at .10 or $1, it mainly attracted $1,000 or less investments. Near the top at $15+ it may have attracted more serious money say $5k, $10k or $20k, but at this higher price they would only fetch you
BTC1,000 more or less.
After the bubble all the way to this January, was a prime chance to buy. Bitcoin had survived the bubble and was cheap. Now the average investor of $2,500 could have bought
BTC250-
BTC500, median investor perhaps half of that, and a serious investor of $100k would have
BTC10k or more.