What would $5 billion buy, apart from a bit of Trump's wretched wall?

Donald Trump has gone on so much about wanting Congress to cough up $5 billion for his south border wall with Mexico that you might think that's all he needs to keep the "baddies" out. But of course that's not the case at all. It has been estimated that $5 billion would provide a wall to fill up only 215 miles of the 2,000-mile border. So there would be a long way to go. Congress knows that if they give in this time and hand over $5 billion, the president will be back to ask for more and more and more until his wretched wall stretches like the Great Wall of China across the whole frontier. But it's not just about the wall. It's the whole concept of keeping people out of the United States by building a massive wall. Like someone has said, it's a Middle Ages idea. Will the US border patrol officers be required to stand on the top of the wall with pots of boiling oil to pour on anyone attempting to climb up? (There will no doubt be a thriving industry in extendable ladders on the Mexico side). But $5 billion is not small cash either. With $5 billion in your pocket you could build a town-full of houses or provide meals for the homeless for a decade, or build one and a half aircraft carriers. But Trump wants his wall because that's what he promised in his election campaign, and this time he seems prepared to hold out until Congress agrees. The government could be shut down as a result for weeks, or months, depending on who blinks first. The wall is one of his great failures so far in his presidency. He managed to get the courts to agree a version of his desired ban on certain people (Muslims) coming into the country, he got his chosen judge onto the bench in the Supreme Curt, he has announced the withdrawal of US troops from Syria, he has scrapped America's involvement in the climate-change agreement and US participation in the Obama nuclear deal with Iran, all of which were his election promises. But there is still no prospect of a wall, and I suppose Obamacare is still running, so that's a failure too. But the wall is his thing! He wants that wall. He needs that wall. Now where did I hear that before?