Price of milled lumber versus cost of logs; general state of the economy; value of Canadian versus US dollar; US tariffs on Cdn wood; mill too darn far from the woods; couldn't compete with third-world labour costs; Jones boys didn't know nawthin' from nawthin' 'bout runnin' a sawmill - when you think about it, there are many possibilities ....

Sump'm like:

Oh, the Jones boys,
They built a mill,
On the top of a hill, [which, if correct, might explain why it didn't pay]
And they worked all night,
And they worked all day,
But they couldn't make that sawmill pay.

Oh, the Jones boys,
They built a still,
On the top of a hill,
And they worked one night,
And they worked one day,
And, oh, how that little still did pay!