You could reasonably say that most cost estimates of Trump's fantasy border wall have been conservative and that the total cost to build and maintain it would be far higher. You could reasonably say that even if you assumed it would be constructed of simple wood and concrete and not draped in golden adornments.
U.S. Customs and Border Protection (CBP) has released guidelines for aspiring designers and their guidelines say the wall must be pretty to look at.
"The wall design shall be physically imposing in height," the CBP outlines say. The government says its "nominal concept" is for a 30-foot-high wall, but adds that designs as low as 18 feet "may be acceptable." [...]
It has to look good, too. "The north side of wall (i.e. U.S. facing side) shall be aesthetically pleasing in color, anti-climb texture, etc., to be consistent with general surrounding environment," the CBP says. There's no mention of the aesthetics on the Mexican side.
In addition to calling for 30-foot-high walls, the guidelines also say it must prevent people from tunneling at least 6 feet underneath it, meaning the wall would actually be 36-feet-tall. The guidelines also say the wall must be resistant to tools such as a "sledgehammer, car jack, pick axe, chisel, battery operated impact tools, battery operated cutting tools, Oxy/acetylene torch or other similar hand-held tools."
Unless they plan to construct the wall out of solid cast-iron, it's not clear how they envision it standing up sledgehammers and blow-torches. But even in that case, cast-iron isn't necessarily pretty and, as you know, the wall must be pretty.
If you're keeping track, the costs are adding up quickly. An "aesthetically pleasing" 1000-mile-long wall that is resistant to industrial cutting tools and extends 30 feet in the air and 6 feet below ground sounds like a trillion dollar project, not $25 billion.
Factor in the costs of materials, labor, maintenance, and the legal proceedings required to seize land to even begin construction and you have a giant, ineffectual boondoggle.
When the city wanted to dig up my parent's backyard (and several neighbors') in my home town so they could make it less susceptible to frequent flooding, the entire process took nearly a decade and that was just a small block of homes. Trump wants to seize and demolish thousands of acres of land, much of which is owned by private citizens. Trump could be out of office before construction can even begin.