When you look at the actual dollar amounts for these campaign contributions, they are often fairly small. They are in the ballpark where any well paid individual (doctors, engineers) would be able to afford a 1:1 coffee meeting with their representative.

This either means that a) buying our elected officials is cheap or b) we’re not looking in the right place to see the actual transactions.

A much more likely (and hard to regulate) form of corruption is “back-door lobbying” where there isn’t a clear payment now but a promise of bigger payment in the future. Such as “you helped our industry do X, so once you retire from congress we’ll reward you with a high layer do—nothing consultant’ role”.