Yes, I'd figured you meant the time involved in getting a successful (i.e, functional) build.
The 'all-in-one' is as much a physical reference as anything - the combination of the Zero and the ESP pHAT is compact and sufficient for testing individual sensors in a neat way - my current setup involves 4 interlocking breadboards which are chock full of circuits and sensors and it's getting a bit like a bowl of spaghetti. A Pi 3 would be a bit of a luxury purely for this purpose and would knock out most of a month's budget set out for project components. ;)
I'll certainly give a try - thanks for the link.
Cheers,
Brian