Not seen the book, and perhaps I mis-read the point... but rather than a mis-print, is it possible they are suggesting that you should really be placing the value on your spare time, essentially using an inverse of your working hours? So if you work 70 hours for $420, that is the price you pay for having the remaining 98 hours of the week as free time and a $ is then worth 14 minutes?

Or perhaps you can use the same maths on the basis that you work to fund your spare time, so if you are spending money and getting less than 14 minutes worth out of every dollar then you are overspending?

It's not necessarily an intuitive way of looking at life, but I can see an element of logic in the approach.