Buying senators is surprisingly cheap. This is why I think there's a huge untapped market for democratized/crowdfunded lobbying. I also think that democratization would expedite its demise, which is the end game that would benefit society the most.
The problem is it isn't just a money thing. A lot of lobbying is about connections, "friends", long time working relationships etc. A random person walking up to an opponent politician with a large check wont get anywhere, no matter how corrupt that politician is. Political funding is absurd in this country, and politicians spend most of their time raising money for the next campaign, meaning a one time check isn't terribly useful to them compared to a long time, implied continued working relationship.