I see your point although that one would be about BMW drivers more.. 
I find it very interesting that you understand the lyrics in a complete opposite way. I know about language barriers (as a German myself) and very often need help in understanding exact meanings of lyrics sometimes. Sometimes one small word can change it all.
Her face being hard as a scaffolder's bar might have been the detail in MK's mind that made the song idea going off for a contrast to her quick little steps, the stiletto boots and her teint. She obviously was a woman thinking about problems in her mind which made MK go imagine how her life would be. I wondered always how the narrator knew it was the Scaffolder's wife and I came to the conclusion that she was a well-known person in her town, you don't know her personally but you know who she is.
LE
Yes. my interpretation is the same as yours LE. I come from a family of people who work in the construction industry and customers paying, or at least not paying on time, is a big problem.
That said, it could be that it's the scaffolder and his wife who don't pay their debts, who knows?
It's really interesting to see how everybody reads (good) lyrics in a different way, depending on your own experience etc. It's like poetry.
Re scaffolders: I remember that around the turn of the millenium there was a series of scandals in various EU countries, which was about hiring subcontractors, who would hire subcontractors etc.. In the end, the customers had paid a lot of money in advance and then the contractors went bankrupt (on purpose), so both the customers and the subcontractors were getting the short straw, while someone else got very rich (Paraguayyyy, anyone?
). This particular scaffolder could be anywhere along the line, of course.
What we do know though, is that MK doesn't like builders, and that might include their families.
