Well, you're not wrong, but also, as of 2018 TSA has 945 of these things in use at 340 airports around the country (according to this article). That's $19,682 per unit, which probably includes on-site in-situ installation, configuration, and testing (in an airport, so all involved techs will either need SIDA credentials or be escorted at all times), plus part of the development costs for the software. Many software contracts also include maintenance and upkeep for a year or two. So it's not really surprising that the total comes up to just under $20k per unit.

I'm not saying that's what it should cost, but it's not all that surprising to see such a price tag on a gubment project. Heck, I'm surprised it's not more expensive.