When the cost of something goes up 20x, one rarely sees demand unchanged at the new price point. I don't believe influence to be so price inelastic.

The representatives become more dependent on their party to win the election and stay incumbent, so the lobbying money shifts to the members in the party leadership who will eventually direct the other members on how they should vote.

The representatives become more dependent on scheduling and organization, so lobbying shifts to those people who control the calendars and schedules.

You can't have a working organization of 9400 people who all have equal power. If it isn't given an explicit hierarchy, one will form spontaneously, and lobbyists will obviously focus on the topmost layers of it.

If there are 9400 targets, you don't lobby all 9400 of them. You lobby the 940 most likely to sway the vote.

How do you figure? Each person would be one-twentieth as influential and important to sway as before (assuming, probably wrongly, that there aren't blocs you can sway by targeting one or two people).