Yeah, money needs money and slums need the poor - that's obvious and I don't know how to alter that beyond a redistributive economic model that currently, isn't en vogue - the point you are making appears to be that we require vast behomoths to essentially bankroll the future. Perhaps...
But ultimately do you not also question the influence that they have on that future in terms of what is invested in and what isn't and do you reach a point where your company is earning way beyond what anyone can really conceptualise, the idea that it's spending is dictated 'by the market' becomes laughable. These companies can shape the market in a way that doesn't necessarily represent consumer demand/need or social demand/need. The idea of making profit becomes self fulfilling because they are the only companies big enough to reach the market or they become the market and thus put whatever they want on the market.
Once you've reached a point where a company/individual can 'invest' with almost total impunity, it is then effectively no different than say, the Soviet military/industrial complex. The rules of capital no longer apply to it. We reach a kind of feudal situation where every company or individual plying their trade does so only with the blessing of the good lord corporate behemoth and they pay their tithes in service charges/get bought out/etc.
Yes, that can fund innovation, but it can also completely distort markets and destroy innovation and competition. The notion that we need insane levels of personal wealth "because things are expensive to make" seems a little simplistic and perhaps also highlights a basic problem thrown up by capitalism (which I don't have an answer for) - which is that cooperation would lower cost tremendously - yes, to make a new car is expensive but all over the world, car manufacturers are doing the same research in silos and essentially designing the same thing with tiny minor differences. Of course, we can laugh and say 'well, what is the alternative? Trabants?' and that's to some extent a fair point - but equally, it doesn't mean we shouldn't think critically about our own system does it?