[kijin]

That hole ain't gonna stay empty for long. It will probably fill with water and provide a habitat for a fairly large variety of plants and animals. Which might or might not be a net gain for the environment as well, depending on what species it attracts.

Middle-class Americans spend more money landscaping their backyard than the cost of this entire project.

[tptacek]

Middle class Americans do not in fact routinely spend $80,000 on their lawns.

[kijin]

Routinely, no.

As part of the total cost of home ownership over a lifetime, a lot of people probably do spend tens of thousands of dollars on their lawns. Especially if they have an HOA telling them what their front and back yards should look like at all times. Much less fun than just digging a big hole!

[eth0up]

With three cars parked on it they might.

[Retric]

30$/ week or 130/month for 50 years ~80,000$. That's actually not that high, IMO.