Actually, there's a much cheaper option if you pay the installation fee of $300.[0] This works out to $25/month over one year. While $300 is a significant amount (especially for people with lower incomes), it is an option and is a fraction of the cost when you look at the long term.
$300 up front is a huge barrier for low income people, who don't tend to have cash reserves. Just for 5 mbps. Also: the wording of the agreement gives Google the flexibility to use the number of $70/month customers as the benchmark.
You can also pay the $300 over a year ($25 / month for the first year), and then get it for free after that. $25 / month is cheaper than the what I pay for my relatively slow internet.
A few years ago I was supervising a guy who was hired to clean up a contractor's mess in a penthouse loft in the building I lived in. Making small talk, he asked me what I though the difference was between rich people and poor people. His view was that it was bad judgement. He told me that most of his (poor) friends had nicer TVs than the rich people whose houses he cleaned.
Given that, I suspect that some of those 'poor neighborhoods' might have a significant number of people willing to commit to spending that kind of money (whether they have it or not) to feed movies to their big new 4k TVs.
https://fiber.google.com/cities/kansascity/plans/