Given your clarification, Congress is easy: Not anymore. The 27th Amendment bars changes to Congressional Pay from occurring during the session the law was passed. All of the House, and 1/3rd of the Senate will be up for re-election prior to the increase going into effect and their opponents will try and use that against them.
As for the people, I'm inclined to say it's harder to peg. There are certainly those who are happy that they get some of that Pork, but I've also talked to Republicans in Blue States who will actually be hurt by the recent Tax Cuts (and they know it) but support them anyway on principal despite that (Basically, one of the things gone in the recent Tax Cuts is the Federal Re-reimbursement for those living in states with high taxes. Depending on your bracket, this can actually hurt you if you're living in a state with high income taxes, like California (where I met these individuals) because you got some of that back from the Feds.)
I personally am a registered independent because I don't strongly support either major party, despite the fact that one party is pretty dominant in my state and they don't need to court the undecided crowd like me (when I lived in Florida, they treated me as if I was a wrathful god to be appeased). It's getting better now because my state has purpled up a bit.
Even still, there are people who will vote for the party that supports their stance on a single issue, finances be damned (Abortion and Gun politics tend to get this a lot, but other issues, for example, environmentalists tend to vote for Democrats (or the Green Party if they don't care about their candidate winning an election) and Cuban Refugees tend to vote Republican because Republicans usually are tougher on Cuba than Democrats.).
You also have the "Yellow Dog Democrats" (the phenomena exists on the Republicans side too, just look at Trump Supports or the Regan moniker of Teflon Ron for proof, but the Republicans aren't really have a catchy term). The idea is the party can do no wrong and will always get their vote, regardless of position. The term comes from the idea that "if the Democrats ran a Golden Retriever for office, it's still a better pick than a Republican" (flip it for the Republican equivalent, but again, there really isn't a related term for it on the Republican side in so far as I am aware). The general difference between this and the California Republicans I mentioned above is that the party candidate is objectively lousy and doesn't really line up with their values... but at least they aren't from the other party.
This probably isn't an exhaustive list, but it's some of a number of reasons people vote.