Is government entitled to waste taxpayer funds?

Governments spend taxpayer funds to achieve what it thinks the taxpayer wants. In the process it sometimes has to reverse or modify policies of the prior administration.

For instance, almost all US attorneys traditionally submit their resignations when a new administration takes over. In such actions the only direct outlay of taxpayer funds happens if the new attorneys require larger outlays than the fired ones.

There are other actions which result in immediate and significant impacts on taxpayer funds. Two recent examples come to mind. One was cancellation of the Keystone pipeline. The immediate loss of jobs for hundreds, if not thousands, of gainfully employed individuals, resulted in an immediate increase in federal outlays for unemployment compensation. And probably a significant impact on federal inflows.

The second example was cancellation of the WALL. This resulted in a much higher direct impact. For instance, see

https://nymag.com/intelligencer/2021/02/what-happens-to-trumps-border-wall-now.html

Direct expenses of cancelling the wall may total over $1 billion. I realize that amount is peanuts in terms of recent covid relief. However, should incoming administrations be held to a normal oversight of contract cancellation just as they are on contract initiation?