That exists: Mayday PAC. Lawrence Lessig organized it last year. They raised $11 million and tried to influence some key Congressional races, but it didn't really work. Now they're trying some different things:
Interesting link, but $11 million bucks is probably not enough to buy even a single Senator, even if his district is an extremely cheap media market.
A recent Senate campaign in one of the nation's cheapest media markets (Jon Tester's) was run for ~15 million bucks[0] in coordinated campaign funds, plus probably-larger undisclosed amounts of "independent" campaign funding through PAC's etc.
In the same cheap media market, Senator Max Baucus raised >$5 million[1] for the coordinated campaign in his final Senate race, in which he ran effectively unopposed. Again this $5 million does not account for his pre-existing war chest from thirty five years of Senate campaigns or the (vastly larger) fundraising of his GlacierPAC or other related "independent" political organizations.
So the minimum single-senator campaign cost is probably somewhere between those two bounds. Therefore I don't regard the core idea of Mayday PAC as a failure; instead it seems like they need to scale it before we can decide if it's workable.
Yeah! None of this one-man-one-vote crap, back to some good old fashioned plutocracy. After all if the top 10-20% own 90% of the wealth, it's only right and proper that they also own an equivalent share of the political power. ;-)
It seems pretty simple to me. If you want your laws changed, pool your money and go lobby the gov't just like every other corporation.