Trump won with a whopping 25% of the voting population, and not everyone who voted for him wanted the wall; many just hate Hillary and took the other option.
"American taxpayers" don't all agree on much of anything. I have seen several people on here claim that a majority of Americans support the wall, but there's absolutely no concrete evidence to support the claim. I could just as easily claim that a majority of people oppose the wall, but all I have to support that is polls (because polls are SO trustworthy) and the fact that very few people I know support it (my friend base isn't a perfectly representative sample of our politically divided America - no one's is, at this point).
I pay my share of taxes, no more or less. Politicians are subject to income tax like everyone else, though there are plenty of loopholes for the ones who are wealthy (which is a completely unsurprisingly high percentage of them). The fact that they're politicians doesn't give them these tax breaks, though - their wealth does.