I don't know where that number comes from, but I'll assume it's the sum of investments and not the sum of capital available for investment since the latter is a bit hard to determine.
I don’t know of any German funds that make venture investments outside Europe though doubtless some exist. Still, if you want to back into the size of the domestic venture funds, pick a percentage (70%?) of the investments made as having come from domestic sources and figure that a fund wants to put all its committed capital to work within the first couple of years, and figure that the total venture pool is perhaps $7B. There are bigger single venture firms a few blocks from my house in Palo Alto. For example I walk past Accel every day to get a coffee.
As you say there just aren’t many companies there being funded, and when I read the local blogs and such people seem to want “the lifestyle” (or hate it) more than talking about building major businesses. To me it’s indistinguishable from people starting a sandwich shop.
That's not the same as the available venture capital. If there are no good investments to be made, the potential venture capital simply isn't (all) invested. So the point that lack of VC is a problem is wrong, it's the attractive startups that are missing. It's the same in Austria - I invested in 2 startups, got a little burned and have since not invested for lack of good opportunities. I've also been asked a few times by a larger German company for my opinion on potential investments, so I know they're looking and can't find anything worthwhile. Funding is not the problem! And the "market size" is only indicative of the (too few) good startups, not of the potentially available capital.
Not to mention that what gets invested in is mostly food delivery, shops and not particularly technical businesses (which are a very large investment sector in the US but aren’t considered “startups”. What gets written up in, say, Gründerszene are companies like the one that would tell you where to get your car repaired.