does anyone know what is the percentage of bitcoins that are exchanged? %10? %20?

I exchange (or risk in different ways) about %10 of my bitcoins. I wouldn't go above this unless bitcoin price went above 1000 Euros. I guess most of the bitcoins are held by people like me (i.e. natural selection, if you are not like this, you sell your bitcoins, your bitcoins end up with someone who is like this)...

So 100 Million euros is huge. You will be trying to buy a good percentage of all the bitcoins that are being exchanged. That will drive the price sky high.

But I guess one important point is that you should probably not buy bitcoins immediately whatever the price may be, and instead have some flexibility. Otherwise you will drive the market price too high before you buy, instead of after.