I mean, in this case the government spent thousands because there was a small amount of circumstantial evidence that suggested there was clandestine communication happening during wartime.

What was the immediate government spending on Japanese American internment, where there was no evidence or investigation into the ~120k people whose lives were disrupted, and who were transported, housed, fed and guarded for multiple years?

Arguably, spending thousands on investigating something specific is less wasteful than the alternatives the government was willing to take at that time.